Hi, just bought a facelift focus titanium, 2011, 1.6tdci, nicely equipped car but the mirrors appear to be dead. The switch does nothing. I have checked all fuses and they seem fine, the plug is firmly fitted in the switch unit. I'm not really sure how to go about diagnosing a modern computer controlled car.... Does anyone have any good ideas, or know a good auto electrician in the northwest?

The switches can get damaged by valetters if the car was cleaned inside prior to your ownership.  I'd try a known good one next if the fuses are definitely fine, although I do suspect it's a fuse if both mirrors are dead. 

Auto electricians cost a lot so in this case it is cheaper to try swapping a cheap & easy component first imo.

or possibly the left-right mirror selector part of the switch. If it's stuck(electrically) in the centre position then neither mirror will move. Try moving it left to right and back a few times