Corsa Gear Shift Problems

Sounds nasty. The symptoms indicate more than just a simple sensor glitch. When you say 'slips', is it happening across all gears, or just specific ones? Have you tried pulling any diagnostic codes? An OBDII scanner might give you a better idea of where the issue is originating. Could be the transmission control module (TCM) failing, or a wiring harness issue. Any recent work done on the car before this started?

Slips in all gears. I did pull the codes; points to control unit issues. Wiring harness seems ok after a quick check. TCM – is that likely given the display's dead too?

Yeah, the dead display really points towards a central control issue. Given it's affecting both the gear engagement and the display, and the codes are suggesting it, a faulty TCM is a prime suspect. The fact that it's slipping across all gears makes it even more probable. Unfortunately, diagnosing a TCM definitively often requires specialized equipment. Based on what you've described, I'd say a trip to a trusted workshop is in order; they can run deeper diagnostics. Just brace yourself; replacement and programming of a new TCM for these older models can be pricey, around 1000€.

Cheers. Workshop confirmed it's the TCM. Quoted 1000€, as you guessed. Bit the bullet and got it fixed.