Revs hanging between gear changes - Ford Focus 2010 hatchback 1.6 tdci

[Touchgenie]

I am posting this in the hope it will help others so the good bit is there is a solution.
The first symptom I noticed was the revs hanging at best and sometimes even increasing between gear changes. They would always drop down again if you waited however this was not a workable solution. This was also worse in the lower gears and when accelerating enthusiastically. Oddly this symptom would stop and the car behave normally after about 20 to 30 mins driving. 
The next symptom was the cruise control would work for between 10 and 30 mins depending on the type of driving I was doing. It would last longer on dual carriageways rather than back roads.
Stop for a coffee and the cruise control would start working again but the revs hanging would be back. 
After a lot of head scratching and some blind alleys including resetting the throttle position sensor I was no further forward. Logic said there was a communication issue between the throttle and control unit.
To cut a long story short I decided to check the clutch switch. My thinking was it would tell the ecu what was happening during a gear change faster than the throttle being closed. Initially I had not given this much thought as the press the clutch to start function worked (mine is button start ie keyless). On the way home I checked the switch would disengage the cruise control - it didn't. Cruise cut off as the engine revs rose as the clutch slipped when I was pushing it down. Looking good, we have a tangible problem. After some grovelling in the footwell the switch came out and there was no connection on the multimeter. Down to Ford for a new switch and on comparing them one was longer than the other.
I fitted the switch and wow, instant improvement. I also did a code read at this point but there were no reported problems. Under £20 all in, 
Now, two weeks later and all is still well. It has fixed more than the symptoms above too. When driving slowly on a cold engine it would occasionally get a dose of kangaroo petrol (or diesel). I had been driving around this but it is nice to have it fixed. The failed switch turns out to have been a broken spring. This meant it did not extend fully and make the needed connection. 
I hope this is helpful as it was a tricky fault to find. There are other causes of course but I eliminated these by reason and road tests.

 

Addendum - I was also getting noises as though the abs or anti skid was operating particularly over rough roads when cornering. This usually happened when the car went light due to the rough or uneven surface. Anyway, since replacing the switch this has not happened so I am keeping my fingers crossed this was linked too