I'd get either:
A 32GB vertex (£115). Will handle OS and some programs just fine, if you need a lot of program space, you can get another later and RAID them.
A 30GB agility (£98). Nearly as fast as the vertex, but cheaper. You probably won't see a difference between this and the vertex, so I'd recommend this more.
Or a 64GB Samsung (£91). Not as fast transfer speeds as the others, but you will still get a "snappier" performance in the OS than a HDD due to the access times. I have one of these, and performance is definitely very snappy. I have all my programs and most of the Adobe CS4 master suite on it, and I still have about 30GB left. I also do not have any games on it. I could make do with a 30GB drive, but you probably would have to buy another later on for the extra space. It depends whether you'll be able to buy another down the line or not.
If you can stretch £50 more, the £150 G.Skill Falcon or Agility would be your best bet. The Falcon is just a rebadged agility, so they'll be exactly the same performance. You get more space per £ with the 60GB Agility/Falcon than you do with the 30GB drives, and you get better speeds.
But whatever you do, don't get the OCZ Solid series. They use a JMicron controller, which makes them stutter and suffer poor performance. Not sure about the Kingston or Crucial SSD's, but I believe they are both just rebadged samsung drives, and the samsung SSD is cheaper.