Hi Gareth,
Thank you for you message i agree with your points, the main reason I'm assuming the gear selector is at fault is my Seat had a very similar issue which was fixed by replacing two bushes on the gear selector cables.
Once I replaced those bushes and tightened the nut (not sure on the name so i will call it the selector nut) The problem was fixed.
What I find odd is that so much work was done on the gear box allegedly but the gear shifter was not addressed or it could be that this was simply not torqued correctly after the work was complete again a lot of assumptions. I do intend to take this up with A clarks but to be honest the car is sweet even with the additional effort changing gear takes occasionally its nice to drive and I'm happy with the car I have no intention of getting shot of the car I will remedy the selector issues naturally it would be nice if someone else can foot the bill.
I was curious to hear of any others having selector issues, perhaps it is a common problem but this car only has 30k on the clock.