Success!
Just for information purposes (incase anyone else has this issue), the router is a Dynamode BR-6004 WG-1, and the Dynamode website is totally cack and hasn't been updated for what looks like, years. With some searching i managed to find out the guts of the router are some cheapo chinese brand, who also sell the router to Zonet. Using the following firmware 'should' have resolved the issue:
BR-6004 Firmware Link
The router didn't die on reboot, but seems to work fine, and VM have indeed reconnected us. Hopefully the Dynamode now wont be sending DHCP rejection messages back to them.
Cheers for all your help dudes!