Does anybody have a standard MG ZT/Rover 75 sat nav unit for sale (perhaps having upgraded to Mk4)?

I've just driven to UK and my sat nav's become all temperamental. Sometimes working and sometimes not. Now it seems to have locked up completely. I'm assuming it's the nav unit in the rear that's failed so I'd like to find a replacement before driving home on 9 April.

If I need to resort to ebay is it a BMW Mk3 unit I need?

Any suggestions please PM me.

Thanks,
Tom