Neighbour using my garage

[ClarissaX]

My neighbour has installed decking right up against my garage along two thirds of it and about two feet off the ground which means my builder cannot now get access to repoint my garage wall on their side. The have also fixed a long piece of wood to the brickwork next to the garage door, I suspect for a garden gate. I don't think they can do this. Is that correct and if so what can I do? The house next door is in the process of renovation.

If they own the land right up to your garage, they can put decking there. If the garage wall is yours, and not a party wall or boundary wall, they would need your permission to attach anything to it. Unless they own it outright, they would still need your permission.
However, as a 'raised platform' the decking may require planning permission. Phone your local Council and ask to speak to a Planning Enforcement Officer.

2ft high would probably not need pp. He shouldn't attach to your wall without agreement though. Surely it is only part of the wall that is difficult to access.

LIZS any platform over 0.3m in height does not count as permitted development and may require planning permission.

info on decking here

Agreed with the 0.3m but just for clarity it's measured from the highest adjacent natural ground level to the development in question (decking)