Yes well it wouldn't surprise me if the regulations were left intentionally vague, especially the new authorisation for TfL
I've been over to take some pictures of the road and the signage and I think the latter is possibly defective.
The bottom of the sign is over 10 mtrs from ground level and therefore it is very difficult to see it clearly from the driver's perspective when turning right from Skid Hill Lane into Sheepbarn Lane, and because of the oblique angle of the sign and the height of it, it is impossible to see it at all once you've joined the road, (unless you are driving a convertible!)
There are no warning signs to be seen when approaching the junction along Skid Hill Lane so drivers are relying solely on that one sign that has been put up on the opposite side of the road, 10+ metres high and at an oblique angle when viewed from the road you are joining the ULEZ from - please see link to pictures
https://imgur.com/a/x6LoZOKIf anyone could possibly help with the best way to put the appeal together on these grounds that would be greatly appreciated.