dont you guys have Asda in the UK instead of Walmart? Don't they have like a "financial center" (really just a counter with cash registers on it) you can send Moneygram bills from?
if so that is the easiest way to get them and if you really cant be bothered to walk outside then hit up newegg and order dual 7970s with the cheapest stuff for everything else but the PSU which id get at least 800W
but the annoying part about it is everyone else is doing the same thing and the difficulty jumps before you can even put the damn thing together.
Pool Mining = slower, steadier rewards. Low reward but you are guaranteed coins. People pool their hashrates together and when someone in the pool finds a block it is split amongst the members based on how many shares they contributed. The larger the pools hashrate the more blocks it will find but the more the reward is split up as well.
Solo mining = you are only mining for yourself. if you discover a block you keep the 50 coins yourself. High Risk / High reward (damn near impractical for bitcoins at this point)