Let the hive mind of Engadget get that for you.
"I've found myself using my PC for a lot of conversations lately, and I'm also considering recording a podcast to share with anyone who will listen. There are tons of USB headset / microphones out there, and I'm hoping someone has some solid recommendations based on experience. I'll consider both headsets and standalone mics, by the way, but I'd like to keep the bill under $100 if possible. Help!"
I probably shouldn't point out that these prices are considered insanely expensive for the UK then. :)
Seriously though, O2's prices in general are completely wacky these days. The up-front prices that they're charging for all phones are terrible in comparison to the other carriers.