More FWIW: I’ve had a significantly sub-optimal experience with 123-reg and dropped the bargepole many years ago. In fact, almost everyone I’ve tried, including Bytemark, has ended up with some level of frustration and manual intervention from support. One supplier even managed to change a domain’s legal owner for a week or two. I suspect a lot of the trouble comes from difficulty integrating with Registry/Registrars’ API.
For me, the stand-out provider is gandi.net – I’ve heard nothing but good things about them for at least a decade – and that’s a bit weird. (I’ve no experience of their web hosting).
(For one-stop convenience, I put the majority of my domains under Bytemark but with the Control Panel glitches - which now seem like a thing of the past - and the lack of Direct Debit it hasn’t worked out as hoped).