Hi Martin,
I would suggest what you do is upload your web site hosting to your eUK account, create the mailboxes etc. and then ask (or do it yourself) UK2 to point your nameservers to the ones supplied by eUK. This will mean your web site hosting will start to resolve from the eUK server. After that, you could migrate your domain if you wanted to but if you can leave it with UK2, you could do that as well. You'll pay eUK for your
web hosting and UK2 for the domain in this situation.