Right, you need to give us a budget and tell us what TV you have.
A very basic system that includes the amps and decoding built-in is the Onkyo HTX-22HD 2.1 system which can later be expanded to a 5.1 system. The base price is roughly £249 for Richer Sounds.
If you need to go lower than that, consider the Acoustic Energy AEGO M for £139.
Of course you get what you pay for.
You might try just going with Stereo speakers. The Audioengine A5 which is a 5" 2-way with 45 watts, is about £249. The 3" Audioengine A2 is about £130. It is possible to add and Audioengine sub to either of these for an additional £243.
It might be possible to get an amp plus speaker system for about £300. But until I know your budget, I'm not sure what to recommend.
Again, I can keep making recommendations, but without a budget it is hard to know what to recommend.