EVOGESSingle Metal Back Box, 35mm, 1 Gang, 1.0mm Thickness for Electrical Sockets Switches, BS4662 Standard, 20mm & 25mm Knockouts, Adjustable Lug, Brass Terminal (1)

This Back-Box eventually did the job but the 'sliding' Fixing Lugs (for securing the switch or socket) had very little movement as supplied. They were very cheaply implemented and had to be freed-off by prising the crude retaining cut-outs apart somewhat - a very poor design, but after modification worked well enough to get the job done. Wouldn't use this product again or recommend it but would spend that little bit extra for a better designed product.

Caveat Emptor - I thought a back box was a back box. These items have no side holes for securing and the alignment slider was so stiff that you needed a hammer to move it (not advisable if you have a plastic socket plate). And you can get 10 of these for about the same price from Screwfix.