There are only around 20 JVC Authorised Digital Service Centres in the UK, that's why many dealers won't touch them. They don't have the skills and access to the Service information. Your nearest is:
DNH Photographic Services
46 Whitehorse Hill
Chislehurst
Kent
BR7 6DL
Tel 020-8295-0568 or 020-295-0133
Fax 020-8295-0730
Website:
http://www.dnhphoto.com/
They also had a branch in Kemsing but I'm not sure if that's still open.
The GR-DVM5 is a bit of an antique by DVC standards so may not be worth repairing, but it's worth a try.