Newbie to the forum so my apologies for my first post being one of need..

Anyhow, as the title suggests, my wife's Superb has thrown a wobbly and occasionally displays the glow plug warning light. Sometime comes on at start up but then goes off when she pulls away, sometimes appears while on the move but then goes off again after a couple of mins. She took it to a local garage. They plugged into it and told her the fault was with the actuator (wastegate). She's booked it in for this Tuesday and they want £320 to replace the actuator.

Being quite a sceptical person, I did a bit of digging around in the net and came across some info that suggests the same warning light can mean a faulty brake light switch (among other faults). My question is this; if too low a pressure (Actuator sticking open), or over boost (sticking shut), surely the car would run roughly and / or go into 'limp home mode'?.. The car runs perfectly, no power loss at all. Very smooth as usual with no noticeable unusual engine characteristics. Would this be the case if the actuator was faulty?

I know £320 is probably much cheaper than what Skoda would charge but it's still a lot compared to a tenner for a brake light switch..

Can anyone offer any experience or advise on this?