There are countless sites where you can register a .co.uk domain name, and I’ve personally tried lots of them. Most of the time, I just register the domain, set up nameservers (DNS), enabled auto-renewal, and forget about it. I’ve never had to deal with any domain-related issues at almost all of the registrars I’ve used as far as I can remember. Price is one of the factors I look at, but support and trust are more important.