your wrong Alazero the fluctuating temperature and pressure of an auto controling shower is (almost always) a result of poor plumbing design or instalation else where in the building, it should be so, that when a shower is working, and other water usage takes place in the building that no alteration to the temp you have set will happen, this obviously costs more, (bigger bore pipes/ pumps/ controls etc) it is common in houses as well, even if there is only one bathroom, you are taking a shower anfd the hot tap is used in the kitchen, equals..... almost instant cold shower, just crap design and instalation, (see Homer Simpson cartoon) very rarely is there anything wrong with the shower fitting. Hotels are the worst places, because they are tight bastards and regularly get it wrong, I was once in the shower (Harrys bar, France near Limoges) and as I was on the top floor of three, the shower was not that powerfull but OK (already a bad sign) as my friends all got themsleves into the shower elswhere in the hotel my one totally stopped, yes it ran dry, how crap is that, the daft thing is I came out all soapy and didnt turn off the fitting, for ten hours the shower was running until I returned later that day and the owener could not understand why the water boilers would not build up any temperature or pressure, I never told him what I found, serves him right.
CLEM