The ACC fault light came on a few weeks ago, annoyingly just after the warranty expired. Having checked the sensor for debris i assume this is probably a calibration issue. How much damage to my wallet should I be expecting?

A few people have had it done on here but I can only remember thinking that I'm glad it's not me paying that amount! 💸

You can ask to them, maybe he can help https://www.instagram.com/vagretrofit 

Well, whilst driving yesterday the warning light went off and it's now available again. Hopefully it's a one off and not an annoying intermittent vdault.