Try namecheap or godaddy or some others. 1&1, although it is cheaper at times, has a horrible domain management interface along with a few other annoyances.
Use a company with a UK office for UK domains. I suggest 123-reg.co.uk, only £2.99 GBP per year (approx $4.30 USD at current exchange rates). For all other extentions (.com/.org/.net) , I recommend godaddy.com. Lots of voucher codes to save money. Until June 2010, you can pick up premium domain extentions for only $1.17 for the 1st year, with the right voucher code. Also, great interface/control panel.
I'm with Brett on this. I'm U.K. based and have loads of domains registered with 123-reg.co.uk. They are a major telecomms corporation in the U.K. The advantages are very Cheap domain name pricing & also their Client Control Panel is so simple & extremely fast (not Go Daddy snail-speed).