No headset (with microphone) comes close to a quality pair of headphones. If you spend a lot of time listening to music, or even playing games or watching movies with a good audio source, it's worth considering buying something of good quality. To me a good sounding, comfortable set of headphones are infinitely more important than the latest graphics card, or a few extra FPS.
Now, decide whether you want open or closed headphones. (Open = generally acknowledged to give better sound, but they "leak", ie people close to you can hear some of what you are hearing, and you can hear people in the room talk while listening to something else).
After you've decided, set yourself a budget and stick to it. There's barely any limit to how much you can spend, and after the 150 pound level you are paying more and more for less and less.
Brands to consider are Sennheiser, AKG, Grado, Audio Technica and Beyerdynamic. Personally I find Sennheiser to be a bit overpriced for the quality, compared to the competition but I have used their stuff for years, there's no doubts about the quality. If I had to buy something today, I would look at either Grado, Audio Technica or Beyerdynamic, and then pick an "open" model within my price bracket.
Lastly, shop around. Because this is rip-off Britain, consider looking abroad, you can get much better deals even after factoring in shipping, vat and import duties.
For your price range I would look at Audio Technica ATH-AD700 (just great sound and incredible value for money, in every way equal to Sennheiser's HD595), or Grado SR125's. Within this price bracket I don't particularly like Beyerdynamic's "open" models, but their closed DT 770s are brilliant.
Then just buy a $5 clip on mic, and you're done.
