I have workmen in my house at the moment and I am so over the moon with the guy I picked. He has not patronised me one single time, listens to me when I explain the things I know about my (ancient) pipework and wiring, and genuinely consults me on decisions. At no point has he asked me where my husband is or told me 'what you wanna do is...'
This guy could burn my fucking house down and I'd still give him an exceptional review.
I used to be a builder and have supervised many a job in the past so I know a bit about what I am talking about.
We had a central heating engineer round servicing the boiler and he started berating me over the fact that the pressure in the system was miles too high. I assured him that no one would have even thought about increasing the pressure in the system (it was so high that the pressure release valve was blowing off excess pressure) and he absolutely insisted I was lying! I didn't take that very well!
A couple of days of deep thought and I had an answer - the only thing it could possibly be was a defective hot water cylinder. The problem then was persuading the landlord, firstly that that really was the problem and secondly that the bill for in excess of 1000€ really would fix the problem.
I should probably add that such systems here are all sealed pressurised systems - so nothing like the abortions with header tanks in the roof that are still used in a lot of systems in the UK. The hot water cylinders are all fed with full mains pressure so they are enamelled steel or stainless steel, not copper.
In the end the landlord didn't need persuading as the outer jacket of the cylinder sprung a leak and flooded the hall!
When we got the defective cylinder out, there were, as I suspected, pinhole leaks in the inner coil of the cylinder that allowed the mains pressure water in the outer part of the cylinder to pressurize the circulating water in the system.
A new cylinder fixed the problem completely!
@girlonthenet