Hi all,
Happy days!
The Mondeo is back, and with a fully working (and very smooth!) gearbox again!
A strange one this. I pulled the gaiter up on Friday night and had a good look around beneath. All visually seemed good enough, although the black plastic "ball joint" on the end of the gear lever could have debatably needed more grease (a thick pink "gloop") on it. No obstructions from what I saw but the gear changes were still as described above.
A fair bit down in this cavern was a red light on the end of a power adapter (looked like one of those 12v ones you stick in the fag lighter socket). Didn't think anything of it so arranged for a mate of a mate to look at it today in his garage.
Turned out that this power adapter was the other end of the Tom Tom (other SatNavs are available!

) lead that pokes out of the dashboard and had been there since I bought the car.
The lead from the power adapter had somehow got loose and was restricting the gear linkages at the gearbox end.
Anyway, about a half hour later and a tenner for some beers and it was fixed. Nice one to R4N S S for putting me onto his mate Geoff (GL Autos in Iver) who took time out from building superfast Cossies to fix my Mondeo!
Tonnes of kudos and thanks to Dan at Fast Ford too who has really helped me out on this, not to mention invaluable help from other members of the forum.
And a big fat moonie to SMC Ford of Datchet for being an incompetent and uncaring bunch of pricks! Sorry but that had to be mentioned. I don't know if the problem happened whilst the car was in the care of Ford but it is rather a coincidence. No way of proving it either way but what I can prove is the attitude and competence of their service dept has been disgusting! The car will never be going back there!
Back to the good news: Tomorrow it's being remapped by Remaps UK (using a Vizeo map). I'll let you all know how it goes!
Thanks again all!