+1 for Gandi, I've only heard good things about them. I've been with fasthosts.co.uk for 10 years now(with zerigo for as long as I can remember as well), I've currently got 20 domains registered with them and I can't remember having had any problems with them.

I do like Gandi, they're quite pricey though. Shall have to compare prices across the board! Zerigo seem good though.

For personal/small setups,

UKReg.com

Domainmonster.com

123-reg.co.uk

All have solid reputations with 123-reg being the elephant in the industry but UKReg and Domainmonster having superb responsiveness and customer support.

I use Gandi and domainmonster.com. No problems with either.