Hello Matt ,,
I hear you ,, My gripe with Garmin is well documented here,, at same time ,, angst ridden tight wad I am,, I also carry a Garmin ,,

http://www.horizonsunlimited.com/hub...in-gps-62780-2

My personal issue with Garmin is their marketing of the units, in Korea. On purpose ,, they delete Korean keyboards from all Garmins sold overseas ,, therefor,, they charge ,, USD 1,400 for your Zumo here ,,
Another issue is when it breaks,, they must be sent to Taiwan ,, their H/O ,, repair cost plus USD 90 for the DHL .
Lastly,, you your self have said , that their software sucks. Maps expensive.
I have been using Garmin here in Korea ,, through hills and mountains ,, my Garmin battery goes dead in 20 minutes ,, Always recalculating the routes,, recalculating,, My Galaxy s2 with GPS and 3G on ,,,always on target,, battery lasts 8 hours ,, and I have the music ,, some 3,000 songs. This is both unplugged of course.
I pay USD 48 a month for UNLIMITED 3G data here, in Korea ,, and when I travel the world,, USD 10 a day again UNLIMITED.

I use Ram box mount usually I have my Android around my neck in my bosom
See the picks here ,,
http://www.horizonsunlimited.com/hub...in-gps-62780-2

Locus ,, will update your map ,, every other day ,, their Vector maps (Basically an OSM map , ,I am sure you are suing it too in your Garmin) ,, I think two months ,,
Some one sad ,, brilliantly ,, we are using this for RTW ,, not to run down the grocery store. Straight line he said.

Again ,, I hear you ,, get a cheap Garmin ,, stick it on your handle bar ,,, smart phone for all encompassing ,,, multifunction ,,,, in your underwear,,I also carry a small notebook,, only because I have to do online banking and download pictures.

Bottom line ,, Smart phones offer far more choices ,, at free cost of the software ,, free internet via wi-fi ,, free messaging,,, learning Russian on it now ,, got instant voice translator of some dozen languages "Talk to Me",, currency converter ,, skype for free phone calls ,, Viber also works ,, love the Kakao Talk for chatting and sending large files ,, camera that matches normal digital camera ,, even got it's own mini tripod,, several EM programs,,,can watch CNN ,, BBC,,,, Listen to the TED speeches "TED air" ,,,keep track of the finances ,, "Global Stock Market" ,, world weather ,, time ,, not just a lip service like Garmin.
I can back up all the files ,, I pay USD 1.8 per month for the insurance,, for two year coverage in case of theft,, breakage ,, or loss,, I get a new one.

Now ,, for some one at a cross road of buying new ,, Garmin or Smart Phone ,,
Go for the Android ,, I say ,, like you said ,, for 150 quid ,, with a two year plan and insurance.