Removal of Lynx 2 Combi?

I have a Potterton Lynx 2 hanging on my wall. It is already isolated from Mains Gas, electricity and water. It has been drained. It's fitted about 8 feet up the wall in a tiny niche so access (for one man) is by a ladder.
I want to remove it and discard it but I cannot fathom how it's attached to the wall. As it's up so I high the tried and tested method of give it a wack / yank / undo everything may not be the best.

Can anyone describe how its attached or tell me where I could find a manual that describes fitting?

thanks