Have your demo evaluated by Piehole
Below is a list of helpful links to approved studios, agencies and rates in the UK
KNOWING WHAT TO CHARGE
ADVERTISING AGENCIES IN THE UK
There are thousands of ad agencies in the UK, and would be impossible to list all of them. We've found a site that has a directory, and breaks it down into area. They also give you the link to their web page and contact details:
TOP UK SOUND STUDIOS
There are a lot of cowboys out there. When it comes to doing a demo or some training, try to get in with one of the top sound studios. These guys work with major advertising agencies, so we always recommend that you try get in with the best where possible.
UK AGENTS FOR ACTING AND VOICE OVERS