When Roy nails up the hole in the fence, he's shown nailing in the board closest to the hole. When we switch to faerie vision, though, he's nailing in the third board from the hole.
Towards the end, Jasmine climbs through a hole in the garden fence to get to the forest. The hole she climbs through was made earlier when a fairy broke through, but in the two scenes the holes are a completely different shape.
When Jasmine's step father is nailing the fence boards, the overhead shows him nailing the third board in but close ups show him nailing the first.
When Estelle finishes her presentation she steps in front of the projector to turn it off and blocks the picture. There should be a bright spot of light on her coat but there isn't.
Just before Gwen discovers her flat has been trashed, we see a short scene of Jasmine's mum investigating a noise in the back garden. When she closes the door again, we get a close-up of the calendar on the wall - it says it is August, yet just a few scenes before showed Jasmine attending school. She wouldn't be at school again until September.
Harry Houdini did not endorse the Cottingley Fairies Hoax for publicity sake, as claimed. He was extremely critical of this publicity stunt.