Hi if it is your Altinator thats gone. I had to have mine replaced and I use JLH Moters of Stafford they are on Silkmore Lane stafford. The chap that owns and runs it Knows all about our Rover 75 .He as work on them for years. He did mine about 2years ago For £288.00 that was a new one and fitting and vat.
I always use them and have my MOT done there He does the MOT himself
There number is 01785 748161
http://www.jlhmotors.co.uk/