I have been trying all the usual suspects but cannot find exactly what I wa nt. It is a spacer to go behind a normal switch or socket plate mounted on a flush box to push it out further from the wall,yet still allows you to fi x the front plate through to the back box. I need one about 16mm deep its t o provide a neat way of running a spur from a socket in mini-trunking. I kn ow they did exist because I used one on a job a while back. BG make a 10mm version do not know if they will stack to give me that additional spacing b ut none of their stockists seem to list it. Screwfix list one in their onli ne catalogue by Schneider but it has a depth of 9mm and according to one re viewer only pushes the front plate out a few mm.
I suppose if the worst comes to the worst I can Dremel out the back of a st andard 16mm surface box and drill out the bushes for the screws to enable m e to screw through to the flush box but would rather not do that if I can f ind what I need.
Richard