£100 later and still no hot water

[ManagersDilemma]

Our hot water has been getting less and less reliable since we moved in 18 months ago. It's practically non-existent now. We finally got a plumber in last week and he said the pressure in our boiler was too low. We need a new part eventually but he fixed it for the time being (next few weeks/months). The pressure has stayed up where it should be but we STILL have very little hot water. In fact, I think it has actually got even worse.

Sometimes putting the central heating on helps; at other times it doesn't. We do sometimes get a bit of hot water without the heating being on.

I can't believe we paid the plumber over £100 and we still have virtually no hot water. How should we proceed? Any advice gratefully received.

[johnd2]

Sounds like he didn't really understand the problem you had, and found a different problem and fixed that (low system pressure)
I expect your problem is more expensive, of you're lucky iut might be a sensor but sounds more like a scaled up heat exchanger.