you still cannot run heater off shower even if you change RCD.
Have you got central heating in adjacent rooms ? there may be pipes running under or near shower room you could put a towel rad in to work off the C/H
Should be no trouble, did you mean dimmers for L/R and Kit. You may need a deeper back box as dimmers need more space. Take wires off the undercabinet light switch and connect together in a block these will then work off the switch on the light. You need to check how many lights will be on each dimm...
