If its your first time going for this sort of thing, get yourself to some of the dealers names you see thrown about on here and listen to some stuff....whilst a demo in the shop wont necessarily equate to exactly how it will sound in your own home, it does at least give you an idea of the kind of power and quality a system has potentially......and whilst buying from a dealer can be more expensive than some of the stuff you can get through online ordering, as its your first time its always nice to get a little extra help from the dealer in respect to how to set it up the moment you get it home, how much cabling you might need etc (although dont pay much for the cabling, £20 at the most for interconnects and £3-5/m for speaker cabling for a system the kind of price you are proposing)...also if anything goes wrong and help on here doesnt, er, help, then having a dealer in a shop you can go back to pays dividends compared to an online retailer who may or may not wash their hands of you the moment the credit card is ok'd....
nice peoples to go to are Sevenoaks, Richer Sounds, Audio-T and a few others......get in there, have a look at the speakers in their physical all, book a demo maybe for a few models, sounds daft but speakers can vary wildly in how they sound and some folks really dont like the way some sound, other people dont really mind too much what they sound like.....
the MA Bronze range is a nice setup, or the Radius by MA......B&W, KEF, Quad and Mission are also all good manufacturers to consider.....there are quite a few more but best not to confuse yourself with too many options quite often, have a looksy at ones you can live with physically (especially important if the missus has a say) and then go and listen to a few.....as for amps, well for AV i wouldnt stress too much, avoid obvious combinations of bright amps with bright speakers (meaning they emphasis the treble) or warm lazy amps with warm full sounding speakers (because it will sound like someones hit the slow-mo button...heh)......but with home cinema any setup you buy around £800-1,000 all in should impress quite happily compared to an old TV or midi hifi
If you can get to Kent, its also worth checking out AV-Sales as they sell the SVS 5.1 pack of speakers that they also sell via the forums here, whilst that will be a bit more expensive once you add on a receiver, its apparently a very good movie package, the sub will certainly impress (i own its bigger bigger brother...heh) and the bookshelf size satellites are apparently very good too.....whilst there though im sure they can hook up a few more conventional names to compare to....
one VERY important thing....dont rush, take your time, a hifi is often for life not just Xmas
and dont let a dealer bully you in to taking something....if they make you an all in offer of some kind and your not sure if its genuinely worthwhile, tell them you need to think about it and you'll call them back then come on here and let us know so we can suggest if its a good deal or you are just paying what most of us would expect to see...