Yes! Finally! A question I can help with!
The front right of the car sounds right for the cruise control tempostat. This works by using an electro magnet to pull a cog onto a worm gear to rotate the electrical connectors that set the system and maintain speed as well as alowing the motor to pull on the cable that, in turn pulls on the throttle pedal. The symptoms you describe to my mind could be caused by stripped teeth on the main gear in the tempostat or possibly a lose electrical connection to the electro-magnet that would cause it to not fully engage. This would result in the system occasionally engaging on the working teeth and pulling on the cable which would, in turn pull on the throttle pedal.
Definitely a mechanical fault though so at least you won't have to dislocate your wrist to remove the ecu! Having said that and knowing these cars I'm not going to guarantee it at this stage!
Touching the brake earth's the entire cc system in normal operation (as a safety feature), hence why it stopped making the noise. If you had pressed the clutch pedal down, it would also have stopped it until the clutch pedal was raised again as this has the same effect as the brake pedal.
Whip the tempostat off the car and take it apart (disengage the control cable and the 3 bolts that hold it to the car body, plus the clutch fluid pot, then unscrew the cover), it's a pretty simple operation. WARNING - take the cover of the tempostat off very carefully as there is a small spring mounted to the main input shaft (that connects to the cable) which can ping off, it took me ages to find it again, let alone figure out where it goes when re-assembling!
If you've stripped teeth then your best bet would be to get another tempostat (£20-£50 from e-bay) as I wouldn't even want to consider where to start looking for a replacement gear! In terms of searching for a lose connection not sure where to start here as I'm more of a nuts and bolts man but I suspect the problem will be clear once you crack it open and take a look. It may be advisable just to go for a replacement tempostat though in either case unless the problem is clear. If you can resuscitate the tempostat, it's worth cleaning up the half moon shaped copper connectors with a bit of alcohol whilst you're in there as it will prolong the life of it and they can get a bit clogged up over time.
Thankfully you can continue to use the car as normal with or without the cc system so not too big a problem.
Let me know how you get on and if you should figure out or retain the exact positioning of that damn spring please, please send pics as I'm not sure mine is correct still!! [&:]
Good luck with it!
