Thanks for all the info everyone! I’ve ordered Oxford soft panniers and have a 35 litre dry bag I don’t know why I thought it was 65 litre haha. I also purchased a pac safe steel mesh net to keep my soft luggage safe whilst not on the bike (will also use a bike cover to deter would be thief’s )Once I get the panniers I’ll be seeing how much room I have to pack and will go from there! Clothing wise I was thinking AAA rated bike jeans causal bike boots and either a leather, textile or wax cotton jacket but not sure what to get just yet! Cheers !

My purely subjective opinion:

Start with a realistic assessment of how often you will be able to do laundry (be in proximity of a laundromat and have a few hours to spare in that location). For every night between laundromats, bring one pair of underwear and one pair of socks, plus a reserve set of each.

Ideally bring as many shirts, but you can fudge shirts easier. Bias strongly towards synthetic sports shirts - August in Spain! - and you can wash them easily in a basin with hand soap, hang them out to dry overnight and wear them the next day. Even if they are still a bit damp, they quickly dry out on your body. (Bonus cooldown method: go into a gas station bathroom, soak your synthetic shirt in the basin and put it back on under your gear!) There are synthetic underwear that you can also wash and reuse like this, but I think with socks you are probably SOL.

Bring at least one somewhat nice polo or dress shirt.
Bring one pair of off-bike pants. I have thin pants out of a hiking/tech material that still look "normal".
One pair of off-bike shoes, simple slip-ons - for around a city or just to give your feet a break. I use a basic ten-euro H&M canvas pair.
One softshell jacket that can serve as both your off-bike outer layer for cold evenings, and as a mid layer if you find yourself in a sudden mountainous snowstorm or freezing rain.
Buffs/neck gaiters to serve as a helmet sock, and additionally as a bandana/head wrapper in the sun without a helmet. You can also bring a sun cap and keep it in your topbox on the assumption that you will always swap it out when storing your helmet.
Plus your toiletries bag, and you're pretty much set.

For the bike - tire plug set and ideally an electric air compressor. I have a previous generation of this, and it's been great. Chain lube - but you can also buy it at almost any gas station on the way (don't worry about chain cleaning, unlikely to be relevant on a one-month timescale). A pocket tool like a Leatherman - useful for camping and basic bike adjustments if needed.

Before you set off, do an oil change and be sure to check your tires! You will be putting on a season's worth of miles in a month - if your tread is getting shallow, you might see cord before you get back. It's a canon event for any bike traveller to do an emergency tire swap in a random tiny town.

Mine's a Revit, but the general recommendation would be a one-piece made out of thick plastic, with a diagonal zipper that has a flap over it. Having an outside pocket is useful for things like highway toll tickets. The old person in me suggests to get one that's fluo yellow for visibility in the rain. Make sure you have a pair of nice waterproof gauntlets (mine are Dainese D-dry) in addition to warm short gloves.

Oh yes, this is not really a hot-country tip, but because I ride in cold countries, I cannot recommend enough a Merino wool base layer (longsleeve shirt and long underpants).

If you don't want to wear your existing leathers, I would recommend getting a textile suit that zips together at the waist, with rainproof and thermal layers that you can remove when not needed, and big ventilation flaps that you can open. Having protective gear that looks like it's not protective gear is a long, arduous, expensive and highly personalized process - I normally ride in Revit kevlar jeans and a Richa leather jacket that looks mostly casual, but for a long tour I still switch to my textiles. It is part of motorcycle touring to teach yourself to stop caring about what others think about you, and understand that it's perfectly fine to walk into a cafe in your moto gear!

Oh my. Two pairs of underwear and two pairs of socks PER NIGHT? I must be misunderstanding.

Another data point: I go many months without going to any sort of laundromat/laundry service, hand washing everything (including riding jacket and pants using a brush in the shower). Modern active clothing is impregnated with some sort of magical substance allowing it to go many days without smelling rank, and it dries easily. I do bring a length of light nylon line to hang stuff from.

Another data point: I don't go on extended trips without some way to adjust my chain. I learned this the hard way. The list of tools to carry can get absurdly long (and heavy), but even if you're willing to stop periodically at repair shops and have stuff done for you, the convenience of NOT having to do so is worth it to me. Exceptions: quick journeys, or trips in the Developing World where repair shops are everywhere and will quickly do stuff that requires advance appointments back home.

I promised myself I wouldn't get into any debates about packing lists, but the underwear/socks thing was impossible to pass up!

N+1, the number of nights plus one extra

Chain adjustment is not likely to be an issue in the first month after a service, even with a lot of miles. That said, I appreciate my VFR's single-side swingarm and the chain adjustment via excentric... the attachment is in the factory toolkit, but I think I've done it exactly once over three VFRs owned. The benefit of Hondas.