it all depends on your needs : -
if you want lots of CFM's (so you then have the possibilities of sandblasting / hooking it to a water supply as a jetwash / dual feed to an airfed respirator) then twin pump is the only way 2.5 or 3hp - comes in lots of flavors ; tanksize, pump type &c
http://compare.ebay.co.uk/like/3707...ff11=ICEP3.0.0&ff12=67&ff13=80&ff14=63&ff19=0
http://www.ebay.co.uk/itm/Burisch-A...Air_Tools_and_Compressors&hash=item257ee572b5 (I have something like this one - it's a beast!)
if its only for medium spray duty but you'd like something that isn't 90+ Db then there are some very good "silent" types but they are still spendy so you'll have to compromise with a smaller tank or bigger budget:
http://www.machinemart.co.uk/shop/product/details/shhh-air-compressor-29
none of the small ones are much good for more than light duty - I had a 1.5hp oil less with a 6ltr tank and when spraying it was pumping almost constantly - it could do it but 95Db constantly for an hour or so in a domestic environment meant I put off using until I had no real choice, the 50l capacity of the one I have now means it's only topping up every 5 mins or more depending on useage.
I also bought a HVLP topfed spraygun, which helped with overspray and reduced the possibilites of laying too much down - you might want to factor that into the cost, plus some sundries; - airhose (the ones that come with, are crap - ok for air blowing but not much else) this will suffice:
http://www.ebay.co.uk/itm/HVLP-Spra..._Body_Shop_Supplies_Paint&hash=item5d40546058 like mine
http://www.ebay.co.uk/itm/RUBBER-AI...Air_Tools_and_Compressors&hash=item43a152d48e
if you buy an oiled compressor you
MUST MUST MUST buy a oil+moisture filter and fit it somewhere closeish to the end of the airline -
http://www.ebay.co.uk/itm/AIR-FILTE...Air_Tools_and_Compressors&hash=item1e77b2052c
maybe with an extra few meters of line between it and the gun - DON'T buy a PoS 1.5 mtr whipline - they aren't long enough and the included swivel connectors leak air badly - go the extra mile (that I ended up doing) and buy a couple of mtrs of 8mm inside dia. hose, some male and female
1/4 connectors like this:
http://www.ebay.co.uk/itm/Airline-H...Garden_PowerTools_SM&var=&hash=item19d7103193
and make it up yourself - oh and if you go the quick connector route; all connectors come in long (like the link) or stubby (half the size) and they don't mix very well if at all sometimes, so find out which ones are fitted to any tools that come with the compressor and buy more of the same, if you don't get tools included then buy a few sets on standby as invariably any extras you buy like car tyre inflator, air blower &c won't match.
and if you REALLY wanted to be belt and braces spraying oilbased / 2pack or nitro shove on of these on the end of the airline before the gun which will squeeze out the last contaminants as 2pack and nitro are very temperamental.
http://www.ebay.co.uk/itm/Deltalyo-...Air_Tools_and_Compressors&hash=item2a2d3390bd
Most of the larger units have dual feed outlets; but if it also has a built in regulator at initial output it will only work with one of the two outlets, so connect up to that one and reduce to a bit above working pressure at source - if you rely on the regulator built into the oil/water trap, the extra pressure there has been known to cause some of the contaminants to get through.
oh and buy PTFE tape - LOTS of PTFE tape you'll need it for all connecting threads, but be aware you'll never get any system totally airtight and lossless.
as you are in cardiff (I'm N Bristol) I'd be willing to lend you my rig to try out for a few days or something if you wanted to dip a toe before committing, but I would require a cash deposit (just in case I'm sure you understand) or at the very least you can swing by and I'll show it to you so you can get a feel for it.
any questions, just holler
