Light work and small panels? I see your avatar picture is a motorcycle, so should I assume that this may be the application?
If so then you'll need a decent gun to start with. I use my Devilbiss Pro Lites for motorcycle parts - tanks, covers, mudguards. For some smaller parts I may use a midi sized gun like the Iwata AZ4. You could use something like the ANI R160 for all these parts but the finish on the larger parts may not be quite as good.
Most midi sized guns need about 4CFM from the compressor, some up to 6CFM. A full sized gun like the Pro Lite will use about 10CFM if fitted with the RP style aircap and over 16CFM if you go to HVLP. HVLP also adds to the requirements for midi guns, by a similar percentage.
But, it's not just your gun. If you use other air powered tools like sanders, blow guns, grinding and cutting tools, and more. All of these have much greater air consumption than most sprayguns. So it's best to look at your compressor needs from the aspect of these tools. Don't use them now? You will later, which is why you should plan for them now.
Tank capacity. Fortunately the UK uses real capacities, as in litres of water. 50 litres is pretty much an absolute minimum but I'd recommend going up to around 90-100 litres. You won't run out of air when spraying but with a smaller tank the air doesn't get any time to cool so you may be battling water issues. It's more expensive but worth it in the long run. Horizontal tanks seem to be more common in the UK than vertical, similar to here in Australia. However, the vertical style is much more floor space efficient and drains better. Go for vertical if you can.
Compressor capacity. I use a compressor that can deliver 475lpm (free air delivery) or nearly 17CFM. That's good for me but may be one size too big for what you're doing. So, look at something with a capacity of around 13CFM as a minimum. Some air tools may not run continuously or you may have to turn them down a bit. I used this size for some years in my shop and it was ............adequate.
Compressor type. A whole range of options here but generally stay away from the direct drive units. If making some noise isn't a big problem then a belt driven compressor is fine but if noise is an issue then there are "quiet" units now available. Unless you have 3 phase power available then stay with single phase - in the UK you can go to 20A which is enough for a 4HP motor and FAD capacities up to about 17CFM. 3HP will generally give you about 13-14CFM.
Air drying. Clean dry air is crucial for painting and running air tools. You should consider a way of drying your air or separating the water vapour that will be in it. There are expensive refrigerated units available that do a great job but an array of copper pipe will be just as effective and save you a lot of money.
Examples. I've linked to Sprayguns Direct in the UK because I buy my guns and some other things from them. Prices are very competitive but you should shop around, of course. Your budget may lean you towards getting the cheapest unit. Generally that is a poor choice, I know, I've done it and had to pay again to get what I really need.
Good.
https://spraygunsdirect.co.uk/product/fiac-air-compressor-workhorse-wr3hp-50p-1/Better.
https://spraygunsdirect.co.uk/product/fiac-belt-drive-compressor-wr3hp-100p-1/or
https://spraygunsdirect.co.uk/product/sealey-vertical-air-compressor-sac1903b/Best
https://spraygunsdirect.co.uk/product/fiac-belt-drive-air-compressor-wr4hp-200s-1/Silent type.
Cost. A big variable but from what I can see, suitable for your needs starts at about 500GBP with better stuff around 800GBP and from there up to 1100GBP.
Finally some thoughts on where they're made. Although there are a few Chinese compressor pump manufacturers that produce high quality, long lasting units most, especially at the bottom end, are rubbish. American made are generally quite good, but expensive with the freight cost. Italian made I've had good experiences with. UK made are probably a good bet but make sure that your retailer supports the products they sell with a full parts and service and warranty backup.