Ok so I finally got to this job an Saturday. They've had someone there fiddling.
Set-up is; oil boiler downstairs in garage/basement (house on hill), CH pumped, HW gravity, programmer by boiler. They had said they didn't want to keep going down to operate programmer if needing to boost HW or put heating on early etc. Engineer had replaced room stat with a programmable roomstat and then set both HW and CH to always on and told them to leave it like that. There is no cyl stat for HW so basically boiler has been cylcing on/off permanently, boiler stat was on 75 deg C. This has killed one thermostatic shower cartridge and one Monsoon pump.
I turned boiler stat to 60 deg c and they have reported that now the water measures 60 at the taps, so that's better.
I have two questions.
1) Will 60 deg C be man enough to heat the house? I know it will do it, but more slowly.
2)If a cyl stat is fitted to turn off boiler when satisfied; when the heating comes on will the fact that this is pumped stop the cylinder from overheating , as presumably the CH pump takes most of the boilers output away from the gravity circuit? (this would allow the boiler stat to be turned up if proves necessary)
I also propose to extend the wiring to allow the original programmer to be sited in the house, as this seems sensible for their needs.