Frozen clutch release arm?

Hi Folks. Our 2003 TF160 has stood still for three years. Before this, it ran well, and we drove it from the UK to France, without issue. We have recently had both sub-frames off, cleaned and repaired, then re-assembled the vehicle. Everything seems fine, except for the clutch.
- The clutch release arm can be moved manually, but is stiff. It does not return by itself.
- All gears can be selected and engaged from the gearstick, whether the release arm is in either position.
- New seals fitted to all clutch system hydraulics, then system refitted and bled.
- When the slave cylinder fork is engaged with the release arm, the slave cylinder does not push the release arm.
I have read that the release arm can become frozen - does anyone here have experience of this? If the arm is frozen, then can it be fixed without dropping out the engine?

Maybe others have better ideas but I would start with a dribble of Plusgas & let stand. After a period a squirt of WD40 (the sperm of satan); it should be moving by now A couple of drops of a light machine oil. Finally something more viscous.
Not too much of any, you don’t want to contaminate the clutch.
I have an old tin of LM grease, over the years it has split into a viscous oil around the grease, every time I’m under or near the clutch arm I drip a couple of splots on.
There is a conversion table which converts old engineers application amounts into metric volume.
Imperial conversions examples:-
2 small drops = 1 drip
3 drips = 1 dob
5 dobs = 1 splot
4 splots = 1 splat.
Etc
Quite straight forward really.
M

Substitute GT85 for WD40.
Available from Halfords usually seen in the cycle department. But obviously available from elsewhere too.
It might not be Plus Gas or Rust Buster but it very thin and doesnt tend to dry out like WD40 might (better add in my opinion).
 

GT85 is made by WD40 - says so on the can. 
What I have found useful is PDFE spray.  -  could be worth a try?  
EBay number  404683580570   This page ignores "paste" for some reason.

I was an avid user of plusgas, however, i read through  this study  and was introduced to RP-90 which scored higher than plusgas, and its cheaper. 

I get mine from Toolstation

Thanks for the info.  Very interesting.

Had the same problem with my previous TF, tried all sorts of lubricant on the shaft all to no avail. But the shaft did became less stiff as the engine got hot, different expansion rates of the metal I guess. The only real solution is changing the shaft, but I put up with it until I sold the car. Fortunately my current TF does not have the problem.

As a general rule, lubrication of the clutch arm should be considered as an annual service item. It is the best way to avoid this problem in the future. 

I have purchased a stainless one, with the grease nipple from Mike Satur to replace mine while the engine is out.

I tried for a good 6 months to lubricate the hard to move clutch arm in my wife's F. I finally gave up and installed one of Mike's SS clutch arms, and a new clutch while I was at it.

I solved this happening on my old F by cable tying an oily bit of cotton cloth to the bottom of the arm where it enters the gearbox.  The tiny 'weep' from the cloth, traveling down the arm, completely stops it siezing!  Once in a while add a drop of oil to the goth and voila!  Need to do this on Felix as I recommission him.

Where did you get the clutch from, i am going to change mine, while changing the arm, and the prices seem to vary a lot