Thanks everyone. They are rotary latches and after a good nights sleep I’m planning to drill a small hole just above it and try to release it through the hole.
Reckon that’s my only option. There is a strip of metal trim either side of the door to the brickwork but not sure what I would be able to see if I removed it.
All started with locking my only garage key inside the garage. It’s a Horman up and over and I’d gone in to get something must have put the keys down and I often lock it by flicking a little catch on the rear of the lock and closing it.
No access from inside the house and my keys are now locked...