@Riley_S It doesn't do anything. 

No light or powering on. There is a slight buzzing inside when plugged in that I can hear if I hold my ear against the top of the M4 but not something I'd noticed before, maybe this is the fan? I've removed it from the network now as it kept saying it couldn't be found and was causing problems. Since hearing the sound I've tried adding the deco back to the network but it won't recognise there being another unit plugged in. 

Do these units often randomly fail? Would expect it after five years maybe, but after two years seems a bit useless. 

There is no reason for a power surge. 

It is plugged into a four way, the only other thing that is plugged into the same four way is a light that I use when I open the cupboard. 

The cable goes through a drilled hole in the wall and into the hall where the M4 has been sitting high up out of reach. 

Nothing else has happened with the electronics in the house in the last couple of weeks.  

  @henrycomb Riley_S

No reply to this? bump.