It's an eco max 824/2 E. I found the cold inlet pipe and it did indeed have a valve restricting the flow. The flow rate was about 3 l/min. I opened the valve a bit to increase this. However, then it seemed to produce no hot at all despite then turning it down again. Moving the HW temperature...
Context is problems with shower. Starts warm, then goes cold and repeats. Have also noticed hot top also does this. I think the HW flow rate is too low. I thought at first maybe just crappy mains pressure, but noticed that hot water flow rate much lower than cold and so maybe boiler heat...