My car has started blipping the throttle when idling

It seems to happen more when the car is up to temp

The blip lasts a fraction of a second and the revs raise to no more than 1200

Far less often the throttle will do the opposite and drop to 800 momentarily

This can happen once every few minutes, upto once every 20 seconds

It is happening more frequently than it used to, and is not generating confidence in the car

Any suggestions? Faulty sensors? Faulty connections?

The only thing that has occurred to me is that the Cruise Control has become unreliable over roughly the same period of time

The cruise installation requires that the accelerator pedal is plugged in to the cruise unit, so my next plan is to remove cruise, reconnect the accelerator directly, and see if that stops the blipping

Failing that any other ideas?