Right, quick update. Had the AA bloke out and had him drive it around for a bit, apparently whatever the problem is it is NOT clutch related. It's either an issue with the actual pedal, or more likely the master cylinder requires replacing.
He said that if I remove the master cylinder and the clutch pedal then feels fine then I'm definitely looking at having to replace the master cylinder. My mechanic the other day removed the master cylinder and said that the pedal then felt fine.
So, it looks as though the fault is solely to do with the master cylinder.
The AA guy said the clutch itself felt great, so hopefully all I'm looking at is a replacement master cylinder.
What I might do is remove the master cylinder myself next weekend (What are you going that weekend Simon?
) and feel the pedal for myself, then if the pedal feels fine all I should need to do is buy a new master cylinder off of Shop4Parts, fit it, and then away I go!
Simon, (The other Simon) the car has done 90K mate. The master cyl is only £50 + VAT anyway so it's not expensive, and the car isn't going anywhere for the time being anyway.