don't limit yourself to South West/South Wales Jonathan, more than likely it will come with a road trailer so you can go pick it up anywhere within a reasonable distance. Don't buy something that requires too much work, I guarantee you'll regret spending more time under it than in it. If its for you and a regular fishing partner go for something between 12-14 feet, any smaller and you'll be loking to trade up within a year and if your budget stretches beyond fibreglass (don't even think about wood) then buy a welded aluminium boat, almost totally maintenance free. Look at
www.boatsandoutboards.co.uk, thats a good source as is
www.ebay.co.uk. Get yourself a copy of Boats for Sale under ?20,000 (or something like that), the small ad section usually has dozens of small serviceable (and cheap)boats for sale. don't forget to budget for lifejackets, ropes, anchors, oars, rowlocks, small first aid kit, any required licence fee etc.