Does the MK7 have a dual mass flywheel? I'd read somewhere that they were going to stop doing them for longevity reasons for the MK7, but never got any confirmation that it'd happened. Dual mass flywheels are living on borrowed time after 80k miles for most marques.
Not sure you can outright reject without giving at least one opportunity to fix, even with something as catastrophic as potential gearbox failure - you'd have to look into that before you give the go-ahead to repair, if you plan on rejecting the car for lack of confidence in it.
Cancellation of the finance agreement does not automatically give the opportunity to hand back the car as suggested on this thread. Finance cancellation is finance cancellation, not car cancellation. For those that cancel their finance, they still have to keep the car (unless there is genuine rejection reason, as may be the case here), but must fund it a different way.