I see now if you have 3 phase available as long as you don't put the oven on the same phase as the shower it works fine. I think you might have to get the poco to uprate your supply otherwise I think you will need to get a decent supply of candles in I really can't understand why European countries don't to the same as the UK and have an 80 or 100 amp supply to a house there's never any overload issues unless you live at the end of a very long line and that's rare
Over here in NZ, AnnMarie, stoves out in the country were fed with 2 phase 400V, mainly to make sure that when you turned the grill element on, it wouldn't knock half the house out during winter.
I personally think that fusing a 240V house at 80 or 100A is out-landish, sure the houses are possibly bigger over there, but I'd struggle to name any house here that has anything more than a 63A single-phase fuse feeding it, let alone 100A.
You mention about being at the end of a spur-line, it is up to the local supply authority to provide either a tap-changer transformer (that changes the voltage when the load on it increases) or a higher HV voltage into your EOL transformer to take voltage drop into account.
