Hi. I have been having a similar problem with my A3 1.4TFSi. It has slowly been getting worse and this weekend it decided to stop running on the M5 (so called smart motorway). Thankfully it restarted and I got into the lay by.
The RAC said it had a low gearbox oil pressure warning and towed it home. The taxi driver said it could just need an oil and filter change. My local gearbox specialist said it wont be the oil, it will be the Mechatronics unit, its a common fault (£1250ish). My local garage said I can change the oil if you want me to.
Advice would be useful as I do not like car enough to part with £1.2k.