email nominet-at-nominet.org.uk
Explain the situation.
If they say 'OK' what you then do is register the domain with e.g.
123-reg, and all nominet do is change the tag on the record to 123-regs tag, so that 123-reg can alter it on your behalf.Once its pointing at their DNS servers its yours to admin anyway you want.
there are three things in play.
Nominet, who control the whole .uk domain. Their records will point to the authoritative domain name server(s), and the records can be altered by any member whose tag matches that of the record. Nominet alone can change the tag, or the person it currently 'belongs' to:
The DNS company - say 123-reg who will maintain a domain server record for the domain once nominet points to them, and will if the tag is correct, be able to alter the nominet record so it DOES point to their servers.
YOU, who can then point the dns actual machine and mail records to anything you like. If its 123 you can for either no, or very little, money have them redirect mail to whatever account you like, if you don't fancy setting up your own mail server.
Hosting is entirely separate from mail provisions and entirely separate for handling a domain.
I fir example run all my own hosting and email on a machine that is nothing whatever to do with 123reg but all my domains are registered there,