I have an Ocean Alpha 240P. I used to have the problem that HW would work only when the heating was on. A plumber came and fixed this problem, changing something (a brass disk-like thing, which cost £25 on the receipt). Now the problem is that even when I have the selection to HW only, the radiators become hot when I use hot water for long(all the radiators). It seems to be going from the correct flow. I called the plumber and he told me that some sort of valve needed tuning or something. The interesting thing is that when I use the wall-mounted controller (instead of the one on the front of the boiler) and put it to HW only, the problem seems to go. Generally it takes time to heat up and then cool down, so I am not 100% sure about the circumstances when the problem exists and when not. ANy ideas what might be wrong?