I’ve bought a bunch of domains in my time, including a few that currently aren’t doing anything but maybe just maybe we might do that thing we thought of when we were a bit giddy that made us laugh so much we bought the domain. I’ve even been accused of domain squatting on one occasion, by someone with a weird surname who thought I was going after just him when in fact I’d bought the domain as a wedding pressie to somebody else I knew of the same name. The people involved were, in fact, related. Oh, how we laughed.
Anyway, there used to be a worry that if you looked up a domain to see it was available, somebody might notice you doing that, jump in, reserve the domain before you, then charge you to buy it off them. This was all soundly poo-poohed as implausible and paranoid.
My vote: 123-reg.co.uk, who are mostly nice people, especially now they’ve stopped splashing David Hasselhoff over their websites. Just be careful not to omit the dash and visit the .com – that’s a different company entirely, and they’re much more expensive.