As can be seen by the varied replies, the truth is it depends on each circumstance what is the best solution. Try to have as many options as your carrying capacity will allow. I take a tent, cost me all of E14.99 four years ago. it is waterproof and more importantly , insect proof.
I also have a folding camp bed. and now carry now summerweight sleeping bag. As I haven't yet ventured out of Europe I have not had the pleasure of dirty accommodation. but the camp bed and bag would be a solution. Even erect the tent to give me a mosquito free sleeping space.
The entrance has a normal waterproof door with an insect proof inside full sized door, and a large insect proof upper panel under a mini flysheet for ventilation.

I ride on a full sized sheepskin, which is great used as a pillow or for extra warmth under my sleeping bag. Usually I carry a very thin light 'fleece' blanket which i can use as a throw over. By jiggling the various combinations I can always sleep at a comfortable temperature. Either in or on the bag, under or over teh fleece or not. The whole lot was probably less than £50. It has all paid for itself long ago, so I do not need to fret over it. I have to add, it would be inadequate for winter or high mountain camping, but I dont do that.

Outdoor gear is as personal as the bike you'll strap it to.. As oldbmw pointed out. A flick through the Argos catalog or a walk to the army surplus store will have you kitted out with cheap gear that will get the job done. But like anything it will have it's limitations. In bike terms ; a Serow 225 V's a KTM 990 adventure. a CBR 500 V's a Goldwing. All bikes that will get the job done...depending on the job of course. And.. different stroke for different folks! (and budgets!)
If you can afford (and want to) buying top end gear will see you very happy with the gear. But it's not necessary. Also what are your priority's? for me weight is very important, and comfort not so much on sorter trips but the longer you will out on the trip the more comfort needs to play a part for moral / enjoyment. Especially when it comes to the likes of a sleeping mat.

Walkabout; yeah my previous post was a long one: Such is the danger of opening the Hubb while in the the boring late shift at work!!! And yeah; 14 sleeping bags is a fair amount but if you started getting people handing you helmets to try and test - I doubt I'd here you saying no! No bother! Ride safe!

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'99 R1100GS - In a suitable shade of black

It's not that life is so short, It's just that we're dead for so long....
"The world is a book, those who do not travel read only one page." ~ Saint Augustin

Take a tarp some rope and a pole. Run the rope from the bike to the pole, tie a knot around the pole then run the rope to the ground and stake it down or use a big rock. Put the tarp over the rope stake it down or use rocks to hold down the tarp edges.

Not the grates thing to sleep in but dry, cheap and light.

I think it would be a good idea to bring a tent, even if it is just a small 1 man tent with just enough room for you to fit in at least if you break down (hopefully not) or cant find anywhere to stay you will have a back up.

Sleeping bags and mats are your choice, personally i would bring a mat at least as this will get you off the ground and insulate your body from the cold. You could sleep in your bike stuff or in your cloths instead of having to bring a sleeping bag. It might not be comfy but at least you will be dry and away from the weather and stuff. Most new 1 man tents pack very small and could be strapped to the bike or stuffed into a pannier

OR

As a few people suggested a hammack and some form of a tarp with mossey net. Very very small, light, and simple to pack. Can be used near anywhere as long as you have a tree or some emoveable object, or you could eve use your bike as a point to tie to. Never slept in a hammack but told it can be uncomfortable untill you get use to how it feels. And the tarp will keep the rain and wind off, and mossey net the mossey at bay.

Again it might not be the most comfy but alot better than laying on the ground.

For a light tent that packs small try the Big Agnes Seedhouse SL1
Sleeping Pads and Sleeping Bags | Big Agnes

Inner is mesh and can be used free standing if required. Great for Star Gazing.

Weighs 1Kg
Pack size 14cm x 40cm = 6.2 Ltrs

Can be purchased in the UK from Hike Lite for £189.

Or try Integral Bug Shelter 12cm x 26cm (3Ltr) - 630 grams with a
Integral Tarp for weather protection 10cm x 20cm (1.5Ltr) - 550 grams
Ultralight Outdoor Gear - Product: Integral Designs Silshelter Bug Liner
and
Ultralight Outdoor Gear - Product: Integral Designs Silshelter Tent/Tarp Shelter

Still trying to decide which to take myself. If I take a tent I believe its worth taking one you will use otherwise as you say an emergency shelter would be fine. Keeping the tent light will allow more comforts like a quality sleeping mat, bag and teddy bear.

Another good website for ultralight kit is www.fastandlight.co.uk. Aimed at adventure racing. Though if you're serious about getting your weight down it's worth a look a the range for some ideas

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'99 R1100GS - In a suitable shade of black

It's not that life is so short, It's just that we're dead for so long....
"The world is a book, those who do not travel read only one page." ~ Saint Augustin

Thanks for the link. Great site and found this. The Nemo GoGo.
1 Kg and packs to 3.5 Ltr. In between Bivy and Tent. Has mesh section so can be left open in warm weather.

Not cheap at £200.
Online Store at Fast & Light - Adventure Racing, Multisport & Alpinism Equipment
Full details
NEMO: Tents including camping and mountaineering tents from NEMO

On my (short) touring trips I alsways considered it very convenient to have either my 1 or 2 person tent with me. The 2 person tent is made by Salewa (a company in Germnay) the 1 person tent by Snowpeak (japanese company??). Both cost me less than $250 - and they are great (Salewa 4 season tent, Snowpeak 3+ season tent). I also got my summer as well as winter sleeping bags (winter bought from Sierra trading post) as well as my sleeping pad, not talking about all the other stuff (cooking etc). It just gives you more options where and when you want to stop and how long you want to stay without looking around for some sleeping/staying space. Pictures can be seen on my homepage.

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I forgot to mention.. one last tip,
always park you bike far enough from your tent so tha if it falls over it does not land on top of you.. ( you wont want a handlebar in your face while you sleep)

I always travel with a 2-person tent. A good one folds up very small and constructs in a few minutes. Tents are good for storing your stuff when you go off for a walk; keeping your food overnight; providing privacy from the hoardes when you are in places where you just cannot escape; a good place to sit and escape the flies/mosquitoes and other bities when you want to read a book or darn the socks (or just escape the onlookers); and I've found they impress cops more and you are less likely to be moved on. You'll find it much easier to sleep in them in hot places too - when you are more inclined to want to sleep on top of the sleeping bag rather than in it. Considering the negligible space they occupy the extra weight/space is not an issue for me. But we tent users appear to be in the minority here...

cheers
Brett

No, I don't think you're in a minority; I have experienced the issues that you outline there Brett and they are all valid - A bivvy bag can deal with some of them, but not all.
In fact, I usually carry both (belt and braces) - but I have gone with one or other (or none!!) - which gives increased flexibility & options in rough camping. On a long trip, you can always post one or other home, as and when.

As mentioned earlier, a bivvy bag around the sleeping bag will give an amount of extra insulation with more still air enclosing you - and if the tent does leak, well no worries!!

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Dave