Hi Andy,
Just a word of warning. I have 2 domains with 123-reg and about a month back I needed to change their DNS to point to my VPS nameservers (hosted with EUK). So I logged onto my 123 control panel thinking this would be a simple task. One of them I changed with no problems. The other gives me an error regarding my nameservers not being in some registry. The error message tells me to simply contact 123's support team by email. Well I've done this about five times over the last month and I'm still waiting for a reply!!
I have no doubt that their services are ok but their support appears non-existant at the moment for some reason.
In a word, you may be better looking elsewhere!
