OK, mine is now fixed!
However it is a bad design (common on many cars these days), the clutch pedal return spring is made from approx 4mm diameter spring steel and the two ends sit in engineering plastic bushes. The bushes have slots in them that the long ends of the spring push into by the factory. However the open side of these slots acts like a scraper so that any grease applied to the steel spring gets scraped off over time and results in the steel 'creaking' against the plastic as it moves.
The use of plastic bushes means you have to be very careful when choosing a grease because some grease/oil may actually cause a reaction in the plastic that makes it brittle or wear out faster. If in doubt get your dealer to lubricate them.
In my case there was very little lube on the spring bushes and I had some white lithium grease in a spray can so I covered all the footwell in paper towel and also formed a ball of rags around the nozzle to stop any grease going anywhere but on the little bush. I would not recommend this as there is risk that it spray everywhere! probably better to just get some white grease and smear it on with your fingers!
I then moved the pedal up and down a couple of dozen times and the annoying creaking stopped. How long for I don't know.
I then wiped away any excess grease off which there was a fair bit from my over exuberant spraying as shown in the photo!
Anyway here are the pictures of the clutch pedal return spring and the grey plastic bush in the bulkhead and the white plastic bush on the pedal itself. I have circled them in red.
It is a bad design because it will need re-greasing often as the bush will just scrape off the grease again after a time. My Land Rover (hydraulic clutch not cable) has a much better design with a fully exposed spring that hooks onto the pedal and bulkhead at each end. One smear of grease on this spring and its hooks lasts 100K miles of squeak free motoring!
PS. I have changed the wording of the thread title and added creaking so that if people search the forum for either words they will find this thread. I hope you don't mind.