i was in mannions on tuesday last that triton is now €229. eurosales in ringsend has the same one for €235 inc vat.I paid €270 for a triton T90, then €200 for the plumber and the electrician was a friend so he did for free, but imagine it would have been another €100 or so.
I got the shower in Mannions in Rialto, think they still have the offer on as it was in November I got it.
To prioritise you can simply build it into the consumer unit (or auxillary consumer unit) when doing the electrical work (not anywhere near 100 euro for this switch, but elcb costs about 30 euro I think).
What happens when they both turn on together, both draw 40 Amps , your main fuse is only 63A.