Thanks for responding Tickettyboo and Bumble Bee.
I had looked at Genuki but the information was exactly the same as Family Search and Find My Past. I was hoping someone on the ground in North Yorkshire may have already found out why there are no PRs earlier than 1788 had the information to hand without my having to contact the Record Office.
Usually PRs don't start to get gaps or disappear until the 1600s unless some catastrophe occurs. In this case I have been informed by the record office there was a fire.
This is a shame because the Bishop's Transcripts of marriages were not a full transcript. Very often details present in the PR were not recorded on the BT.
In the case of Kirby Misperton the Marriage BTs up to 1781 had names, his occupation, her marital condition, residence of both parties, date and method (Banns or Licence)
In 1782 there is a change in the recorder. He records names, date and method. Witnesses were rarely recorded in the BTs.
So I'm still looking for the marriage of George Spenceley/Spencelay/Spensley and Martha which, according to my timeline above, must have occurred in 1786 or 1787. It is not in the BTs but there is always that nagging feeling - it could have been omitted.
Venelow
Canada