Where can you get an ATA/TIR carnet stamped?
Some of the Inland Border Facilities can stamp ATA Carnets, and can be the Office of Departure for transit movements.
You should tell HMRC in advance that you’re attending an inland border facility if the goods you’re moving:
are going to an office of departure or office of destination (starting or ending a transit movement)
are covered by an ATA Carnet