When i turn my electric shower temperature up the water pressure has just started to fall!!?

hi folks as above having problems with my electric shower! is a triton ivory 2 it all of a sudden stopped working the other day.. gave it a bang and it came back on !! but now it seems that there is just warm water coming out at the same setting it used to be hot!! so having to turn it right up to get a hot shower which results in a loss of pressure as the temp is turned up full so it just is more of a trickle now . had the cover off obviously mains isolated and checked all connections all seems fine??solenoid?? or is it time for a new one?? thanks in advance