In order to map my route, I used a copy of the Ordnance Survey map, produced for the 200th anniversary in 2005. This shows the route the post chaise would have taken, though not the location of the plaques.
I did a lot of googling, a lot of hunting online and found information for around half of them.
When I got to some of the stops on my ride, the plaques in some cases had either been moved or weren't at the location at all, and so to make it easier for everyone who wants to follow the route, I thought I'd create a simple post listing all locations.
Obviously this is relevant as of 23rd October 2017, and could always change again!