Spinycactus
The Windsor Foresters fencible cavalry regiment were sent to Scotland to quell the riots which followed the introduction of the Militia Act in Scotland, I believe they were based in the Perthshire and Angus area.
My 4xgreat grandfather Stephen Shepherd was a member of the regiment when he married Helen Gourley in Arbroath in 1799, there was also a murder of a George Douglas near Montrose in 1799 which was carried out by Joseph Cope a corporal in the regiment.
Hope this helps to narrow down the search area for the marriage between John and Jane.
Donnie