I've just fixed the same problem in my disco. Fair chance it is the switches not ECU. They can be pulled to pieces - just ease a thin screwdriver blade in the bottom and ease the inner out past the locking tabs. Inside they have two rockers and contacts which are easy to pull apart - you'll probably find the contacts gummed up. A clean up with a cloth and a nail file works a treat.

Of course being a rover - it could be any one of a hundred other things!! I reckon the switches are a safe bet - costs nothing and takes only half an hour to find out!

Cheers