You are giving a tough call because right now not a lot of phones are running ICS. As far as I know, there are two types of phones with ICS:
1. Phones launched with ICS: currently only the Galaxy Nexus, HTC One X, S and V. I am not sure when the One V will reach UK as well, but wikipedia says it will launch on 26 April.
2. Phones upgradable to ICS: You have more options in this category, and some of them are already running ICS. If you really have to get ICS now and are on a tight budget, you can give HTC Sensation, Sensation XE a look (probably Galaxy S2 as well). My Sensation is now running ICS and I have nothing to complain about it. Compared to the One V, the Sensation is way more powerful.