combi boiler & London shower company shower

we have just had a London Shower Company shower fitted in our new bathroom. (no shower screen at this time due to a problem with the order but that's another story)
now the plumber turned up the hot water temp because he said it needs to be hotter for the shower to work correctly. this now means that our hot tap water is very hot. (we had it at a pleasant temp before the shower was installed)
is the plumber correct?
the shower is a triple thermostatic valve, 5" head.
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