Just thought I'd let you know about the service I received from the above seller, in case anyone is after greenhouse spares. I contacted him to check which door spares I should be buying and this turned into a several message-long correspondence with someone who has forgotten far more about greenhouses than I will ever learn. As a result of this my door is now correctly assembled and moves much more freely than it did, and I have new door seals as well.
Thoroughly recommended.
Adrian