Hi Craig.
The guys on RT have come back with a result. The wheels are called Phoenix Alloy wheels.
You can see them here.
http://www.rimmerbros.co.uk/pdf/mgro...soryImages.pdf
Rimmer bros might even sell the wheel nuts???
The guys said any 200/400 wheel nuts would do. Apart from the ones you have! It might have to be from a mk3 Rover???