Sorted out I think on Tuesday. Have waited to reply to see if the "work" produced a sustainable result and so far it has.
Maybe down to weather warming up [sic] but on the face of it low temp was not the primary cause becuse the heater had always been on and clutch not returning fully even in toasty car.
Anyway dealer who sold me car 2 months ago had said they'd had the assembly off and cleaned it up etc 'cos it didn't return well when I bought it. Not sure I beleive this owing to the difficulty of really getting in there and so much to remove to get to the components to get the assembly off, disconnecting hydraulics and what I found later
So I did the following: Removed the trim under the knee airbag [2 plastic nuts] for easier access; loosened slave cylinder mounting bolts to allow some play in the pushrod/pedal linkage. Sprung pushrod bearing off the pedal bush gently with a flat blade screwdriver and found the bush bone dry and cacked up with dusty resdue
. Cleaned it off then put good old fashioned LM grease on bush. Put push rod link back on pedal and tightened up slave mounting bolts. [Previously had the slave loose to see if I could ascertain where the binding was and it was not in the slave assembly as that was free and loose]. Checked tightness of main locknut on the pedal bearing and this was OK and pedal free running. Checked clutch pedal return switch push rod was free running and light - it was. Made sure all the wiring loom went well away from pedal linkage [it did not before
] ie thick loom to an alloy control box of some sort and small loom to pedal switch was rerouted to approch the back of the switch more from the back of the switch than the front as previously. Reconnecting electrics to the pedal switch is easier from under the raised steering wheel and going from the drivers position - can see the back of the switch by lifting a fabric cover under the column. Ofcourse I disconnected battery and left it a couple of minutes before disconnecting the "control box" connector in the car as I thought it may be associated with airbags. And had to remember to wait 5 mins after reconnecting battery before putting fob in to allow all the electronics to recalibrate? Says do this in the manual - air con heating flaps reset to correct position etc.
So what do I think the cause was on my motor? poor lube on slave pushrod/pedal bush in addition to wiring to clutch pedal switch getting in the way. It won't need much to foul up that final inch of return movement. The return force is minimal and it is working aginst the return switch spring - which I admit is very light but there all the same. So with the addition of some fabric wound wiring getting in the way that last bit of return movement is a bit of a challenge!