The gearshift is cable operated so unless one of the cables has been kinked or crimped, they shouldn't cause the stiffness. Where the shift mechanism enters the gearbox there's two levers that operate the 'box internals that could cause stiffness if they're sticking but both are unlikely causes.

What service was carried out ? If the gear oil was changed, was the correct grade used as if its too thick that'll cause stiff gear selection (as will not enough oil). Is it definitely the gear shift that's stiff or the clutch operation, crunching into gear as opposed to the actual gear lever being difficult to move ? If the brake fluid has been replaced, possibly the level was allowed to drop too far and the clutch system may have had induced some air ?

It seems strange to me a garage would purposely 'knobble' your car in the hope you'll buy a newer one from them. Taking into consideration the mileage, it is just possible that it's coincidence this has occurred now. I'd be inclined to get a second opinion from a different, trusted garage ( yes, there are some out there ) first and take it from there.

Good luck, and keep us updated please.

Morton - Your description of the twin cable gear shift led me to Google as to which engine this is, and it seems that you have the same PSA engine as fitted to the Ford Fiesta (and other cars). Now - there have been numerous posts on this forum regarding stiff gear change on the Fiesta. If you have got the same engine and gearbox, then you've got the same problem, as I still have to a much less extent now that my Fiesta has done 187K miles of mostly town driving.

According to the posts I've read, the problem has been found to be the nylon bushes on the gearbox end of the cables. One contributor said that he'd got the bushes out and reamed them through to clear the problem. Mine have never really got bad enough to warrant doing that. The stiffness tends to come on during hot, dry weather, and miraculously clears on the first cold, wet day. You could try flipping off the plastic cover on the front of the gearbox, and spraying the cable end pivots with Duck Oil -- and report back if it works or not.