If I was looking to buy a car then I would rather see an invoice for the belt being done over a stamp in the book anyday.
I don't think they do.Just make sure you keep the invoice that should clearly state that it's been done for your records.
Had the cambelt changed on Monday but noticed they didn't stamp the book.
The GTD is like a blow up doll. The GTI is like a proper woman. Sure the doll might last longer, and the woman might have higher running costs, but which would you rather have?