Scooby Soon!

I have a site hosted in the UK using a .co.uk domain, I have a new updated site that is just about finished on a USA host. I need to change the nameservers of my current domain to point to the new host ( in the USA). Only problem is my current host wont let me change the nameservers so i need to transfer the domain to another uk host who will just handle the renewel of the domin every year and allow me to change the nameservers and still be able to log in to admin to update them as and when needed.

I would like to set up the nameservers with the new domain company before I start the transfer of the domain to minimise downtime (and lost £££'s!)