So, up down movement is sloppy due to the pictured plastic bush. 
However, comparing the up down bush to the left right bush, there is seemingly very little difference and indeed swapping them over suggests it is not so much this bush as the plastic L shape housing they sit in. 
this is fixed to the selector shaft by what looks like a roll pin which I simply can’t remove. Awkward access and it just won’t budge. 
if I could remove the housing, my plan was to build up the worn sides of the housing with black nylon and fit 2 new bushes. 
or can this black housing be obtained and replaced? 
not the end of the world but would be nice to have a firm gearstick once again. 
clearly previous owner was heavy handed with the gearstick. 

Any experience fixing this issue welcomed. 
 

K

 

Oh well, I’ve just partially answered my own question. 
Here is the part I need. 
Now I just need advice on best way of removing the roll pin that keeps it on the shaft. 
 

It’s actually this part. Similar. 
But I’m still struggling to remove the roll pin. Does it come out either side if I can find the right diameter pin to knock it out? 

Solved. A 6mm sds drill bit was perfect for knocking the roll pin out. Replaced the housing and both square bushes and the gear change is like new again. 
£20 for the parts. 

Kevin, "Sloppy Gearstick"  - have you ever driven a Hillman Imp ?