Just looking for some advice on mileage correction.

My Audi is some 6000 miles over the 24,000 I agreed to when I got it on finance, so it's gonna be a fair wedge to pay the excess.
Someone told me about correction but I'm wondering if I can get rumbled.
I had it serviced late last year (not at a dealership) but they didn't stamp the book saying that it isn't done that way anymore, so is there a record kept somewhere on the car?
Would the person who 'corrects' the mileage have to alter the service record also in the on-board system so they tie up?

Any advice would be great, thanks.