Citroen Xsara Picasso high revs. very high at idle

I'm sorry but I can't be much help.
This needs systematic testing by a decent mechanic,
which you clearly don't have!
Best guess is a fault in the throttle pedal sensor.

Could try cleaning throttle body in case of possible sticking ,

Hi it's had the throttle body cleaned and the butterfly bit returns normally.

Revs goats back to normal if you turn off engine and restart

any other ideas please its not the idlel control value, had a new one

It is very easy to put the Idle Stepper Motor back with the plunger partly depressed and I have found that this will cause the problem to continue. As it is easy for a home mechanic to do I suggest the you take it out, gently pull the plunger out, clean the inside of the housing with kitchen towel and put back. It is held in with 2 star headed screws. Also suggest replacing the MAP valve at the front of the housing (£12.50) very easy to do. It is the amount of Air that is being let into the engine that is causing the problem and it does not show up as a fault code on diagnostics.