"I bought 2 Crabtree Touch Control Dimmer Switches to replace bog standard light switches. When I unscrewed a switch from the wall, I saw immediately that the lugs on the metal box in the wall were going to prevent the bulky electronics at the back of the touch switch from entering the box.
I replaced the metal boxes in 2 rooms with plastic boxes bought from Screwfix and what should have been a ten minute job took over an hour (not counting the return journey to get the plastic boxes). Even with the plastic box, the wires had to be squeezed in and the switch did not fit snugly against the wall.
I switched on the lights - which was a chandelier of halogen bulbs (10 x 10W) and they flicked and did not stay bright.
I tried the other touch dimmer switch and the result was the same - that they are no use with halogen bulbs.
I bought touch dimmer light switches from a high street store (more expensive) and the electronics at the rear was less bulky and would have fitted comfortably fitted into the metal wall box and I had no problems with the halogen bulbs.
It is a pity that I had disposed of the receipt so I will not get my money back!
Too bulky to fit into a metal wall box and won't work with halogen lights."