Rover 800SE Heater blower problem

[Ipaqowner]

I have an intermittent problem with the 3 speed heater blower on my car...the blower will switch on at the fastest speed of its own accord and nothing you do with the air conditioning/heater controls will stop it...if you go over a bump it will sometimes stop so I think it is probably a poor connection somewhere.
Can anyone tell me where in my car the blower speed control module is located? I found a page on the web devoted to the Rover 800 and it suggests it may be a dry joint or faulty transistor on this module...if I can get to this module I can probably repair it myself as I am a electronics engineer.