Hot water problems with Ariston Eurocombi boiler?

In short, my boiler will only provide hot water whilst the heating is on, the rest of the time it is either luke-warm or freezing cold.

The boiler is currently set to a winter setting, allowing for control of both the central heating and hot water. When the dial is turned for the heating the distinct sound of the boiler turning on can be heard (exactly the same as noise you get when the thermostat is adjusted) however, the same cannot be said for the hot water dial. Turning this dial to max does nothing for the boiler (no noise, no flame). Is this a common problem with these boilers and is it easy to fix? Am I on the right track assuming it is a problem with the hot water thermostat?

Thanks in advance