uk.com domain problem!

I have just registered a uk.com domain (i.e. example.uk.com) for a client, and understand that this is a subdomain of uk.com.

The problem arrises when I try and transfer the domain to my webspace, and I get the message:

"Please type in a domain name without a subdomain."

Which obviously I can't do because it is a sub-domain.

Has anyone had experience with a uk.com domain??

Can anyone suggest how I can point this domain to webspace because I've had no luck!