Move
It's the only correct answer where 123-Reg are concerned - leave them.
They're completely crap - it took them months and multiple failed attempts to figure out how to delete my account when I left them, they couldn't even get that final interaction right, let alone the actual services I'd been paying them for
I tweeted about it 3 weeks in https://twitter.com/bentasker/status/1232363790366232578 - but it didn't really speed anything up.
The underlying issue was they still had products linked to my account, despite nothing being visible in the control panel, and couldn't work out how to unlink it.