Slim jim - Cheers dude, looked at this. Nothing wrong with the linkage or movements, all works fine. The problem appears to be internal, I am guessing that whilst the linage and movement of same works fine, it is not 'throwing the engaging rod'? inside the tranny.
The rod which is attached to the external linkage and drops down, vertically, into the casing then connects to a second rod/hook which is pushed left and right to lock in and lock out the transmission yes?
I believe it is the linkage between these two rods that is failing.
Can the separate? Are they circlipped together or something and this clip could have failed? Could the vertical rod have jumped out of the notch in the horzontal rod, perhaps because someone hit it with a hammer
I think my only next action can be to open up the old girl, but this is more than a tad worrying, its my only vehicle after all and needs to keep mobile.