If I've bought and had a thermostatic valve installed, then that should mean that the water temperature does not fluctuate unless I actually change the temperature myself ... is that right? We've only had ours a couple of weeks and yet it tends to go cold on me for no apparent reason.
My Polish builder shrugged and said it wasn't the thermostatic valve, it was the English houses' pipe system ... I don't think he's trying to pool the wool over my eyes as such, but I don't think that's right!