I have now cut out another hole and fitted the thetford access door.This job was a bit tricky as I didn't have a template or any instructions! Managed to find a pdf file for thetford toilets, this gave some measurements and instructions.I then made up a cardboard template for the cut out size and a bigger template for the overall size of the door and frame.
I wanted to get the door as low as possible without cutting into the black plastic trim strip on the side of the van.After a lot of measuring I marked up inside and out and drilled a hole.Moved the whole thing 10mm towards the rear wheel arch and cut it out.Then I made up a wooden frame to go inside the van to put a bit of strength back as a strut had to be removed, where the door was.
Then I cut the piece the piece of metal that came off the van, to fit inside the door.Top tip when trimming the piece of metal is to cover the side which will be facing out with masking tape. This is because when you cut it with a jigsaw the metal shavings scratch the paint.