At odd times through the last few weeks the gear lever seemed stiff. Decided it was me losing the plot and didn't worry. Yesterday it was stiff and then jammed in gear. Fearing the worst I started going through the linkage. Cleaned out the area at the bottom of the gear lever and found that jammed into the nylon rings was the tag from the gaiter (the bit with the part number etc). Never heard of this before, but if anybody is having a similar intermittent stiffness, maybe it's worth checking that the label is still sewn into the gaiter.

Gearbox oil change. Synthetic and syncro friendly

No, No. Please read again. Nothing wrong with gearbox. The label from the inside of the gaiter had become detached and dropped into the nylon rings on the selector. Your reply does make me wonder however about the posts in the past where people have changed the oil to no avail after getting similar problems or have had garages state "no problem found" or "you need a new box/clutch/linkage etc and that will be £££s".

oops yes, a hasty read, sorry , thanks for the info that might well help one or two on here in future.