1985 Gti Cabby, 5 speed, 2.0 8v engine, sudden change in gear change, hard to select gears

Hi All
was our for a drive today in my new (to me) cabby.  Have driven it several times with no issue and the gear change had been very precise, not too loose or hard, no issues with selecting reverse by mistake… perfect in fact.

After a 20 minute spirited drive, got back near home an noticed it very difficult to find and select gears.  Movement of the shifter is suddenly very stiff / reluctant and its v hard to determine which gear you are selecting.  Gearbox appears to operate correctly in all gears once they are engaged, but it is almost impossible to drive it on the road safely.

So what have I done??? The sudden nature of the change (I think) precludes simple wear and tear being the cause, other than something somewhere must have fallen off, become disconnected or failed somehow?  It might have been my imagination, but at rest, in neutral, i think the gear stick is sitting further left than it used to.  Perhaps a bush has broken or I've lost a spring?  Should I even be checking engine / gearbox mounts are in place (considering it has an engine swap)?

Any pointers gratefully received. 

I would agree, soudns liek a linkage issue start here:
Gear Change Linkage - The Mk1 Golf Owners Club

Thanks, I'd spotted that very useful looking "how to"…. guess that will be keeping me entertained some time when the weather is a little better!  If it is still intermittently stiff after changing all that, then it must be engine mounts.

Any ideas how to test effectiveness of engine mounts?

one way is to put the handbrake on and have a helper put it in 1st and lift the clutch to the biting point. if the engien tries to leap out of the bay you know your mounts want looking at

Don't forget to also check if its a clutch issue, for example could be a frayed clutch cable or the bulkhead where it passes through has fractured - a not uncommon issue.

Or even clutch cable at the gearbox end at a funny angle and sawing it's way through the gearbox.

Thanks for all the suggestions.  Will check them all out when I get a bit more time (and sunshine!)

The problem has almost not recurred in the past few days so must be something transient (and minor I'm hoping)
Cheers