Just to add to this Andy...
If your end goal is to move away from interhost and host all of your sites on EUK then you need to forget about setting up nameservers on the interhost VPS (because you're going to ditch it anyway!)
I'm assuming you've probably only got the one domain that you're really bothered about and that's sound-designs.co.uk. Ok, if I were you at this stage I'd do the following:-
1. Setup sound-designs.co.uk as I have explained in the post above on the new EUK VPS.
2. When you are sure that the site is running correctly and you are ready to change over setup two new "personal nameservers" on the EUK VPS. I call them personal nameservers just because they are running on YOUR VPS and not some other server somewhere.
3. Now we need to register these nameservers with the DNS network. To do this you need to go to the sound-designs.co.uk control panel (at the registrar). The method for registering these nameservers varies depending on the registrar so if you let us know who that is we can give you some more help on that (I'm assuming it's not 123 in this case??).
4. Once the new nameservers are registered you can simply change the nameservers for sound-designs.co.uk itself to point to ns1 and ns2.sound-designs.co.uk.
If the registrar IS reg-123.co.uk step four is actually done as part of the nameserver registration in step 3 but I'll explain that in more detail once you let us know who the reg is for the domain.
My fingers hurt!!
