I,m glad my advise was able to help you, and solved the problem you were experiencing.
But has i have already said, when i have come across this fault, reprogramming the PCM has *NOT* fixed the problem.
As you have found out the cars in question drive perfect on the road and show no other faults, except when the MOT comes around you cannot hold the RPM in the fast idle rev band.
Most customers live with this and MOT test stations are ok with jacking up a road wheel and spinning it.
On one occasion I had two focus 1.6 one was 2000M/Y was 2001 M/Y.
The 2001 M/Y had the problem described , i swapped the PCM's over and it solved the problem.
So from that I have concluded the fault must be a Faulty PCM (Hardware).