Okay, As a bit of an update and hopefully closure to this thread as it looks like the CEM was at fault all along (slightly water staining and dry solder joints) and the recent non start with the "Brake Failure" message led me to look at the CEM again. The CEM has been repaired and all seems fine.
The car has now ran perfect (touch wood!!!) and back to normal. It's recently been on a long road trip to London with no issues.
However I've since purchased another vehicle so my pride and joy Volvo V50 will be coming up for sale very soon.
Thanks to all for your help with trying to diagnose my issues it was greatly appreciated.
