I know where you're coming from.
In which case (I see you're in Edinburgh ... same here) Richer Sounds is probably your best bet.
If you buy the amp and speakers, throw in a bit of humming and haaing and general banter, you can try and get the speaker cabling off them for free! (I did! .... long time ago buy I was buying a DVD/Amp/Speaker package much like yourself)
I'd try and go to you maximum £300 as well. If you want good AV gear, that will last, spend as much as you are able.
In which case, I'd have a look at:
http://www.richersounds.com/showprod...d=SONY-STRK880
With
http://www.richersounds.com/showprod...ANN-EFX5.1-SIL
Mate of mine has a very similar setup and it sounds pretty decent. You also have the scope to add an extra rear centre with that amp if you wan to do so at some point.
You're not going to get a 7.1 amp without breaking you bdget considerably.
For me, next step up in speakers would involve buying them all as separates (floorstanders etc) and you're not going to able to do that on your budget either.
Have a browse round the RS site. There were a few other amp/speakers combos that fitted your budget but, for what you want to use it for, and the amount you can spend, the two above would the first two I'd look over instore.
Speak to the guys instore as well. You may pick up a stray clearance item if you're lucky. Nothing on the website for the edinburgh stor just now but you never know.