Glow worm ultimate 40ff ultrahot water!!!!!?

Hi, I have the above boiler with potterton ep3002 timer and potterton room stst with hot water cylinder stat and 3 way motorized valve, honeywell, pumped. My problem is that the hot water is ultrahot and the radiators come on when the hot water is selected. so i gety both hot water and heating at the same time. I have check the motorized valve for operation and this seems to move to the correct positions. I was advised that the timer was at fault which was a potterton ep2002, upgraded to ep3002 now, but the problem still present. I have had to close all the rads dowm in order for the home not to be an oven!!!!! Any help really appreciated.