Try these guys in Bracknell Berkshire.
They have been trading for at least 25 years and used to be known as 'XRN'
http://www.classic-and-modern-engine-servi...co.uk/index.htm
Maybe behind one of the footwell kick panels?
That said normally these switches are accessible without having to remove panel trim.
On the RR it is under the passenger seat with the ECU under the dirver's seat. If the ECU for the Disco' is up under the dash then the cut-out shouldnt be too far away
I seem to remember from an old Jaguar that there are micro switches inside the wiper motor that determine the park stop position. Worth opening up the motor to see whats happening
There are two distibutor caps for V8 engines with corresponding rotor arms. The difference relates to the height of the cap and therefore how much clearance is between the top of the rotor arm and cap brush.
It might be that you have a low height cap with a high cap rotor arm - this would certainly place excessive pressure on the brush.