Combined hot water/heating system Glow Worm Micron Problems??

Hi,

I have just moved into a new flat. There is a small boiler (Glow worm micron 50ff) which (oddly) is in the bedroom. Prumably for noise reasons it is boxed in and takes time to access.

It is controlled by a simple electric timer in the airing cupboard, where there is also what I believe to be a hot water tank.

The problem I am having is that the only control I have is to turn the boiler on/off (via the timer), and adjust the main therostat on the boiler itself. I cannot separate hot water and heating. If I want a hot shower I have to turn the whole system on, which heats all the radiators- which will suck in the summer.

Do people ever build systems like this?

Can this be right? I can't find any other controls anywhere and I am assured by an amateur plumber friend that it is very odd.

I have thought about just switching the 3 radiators off at their valves, but none of these lock down properly, and always heat up if the boiler is on.

HELP! Is the best solution just to get the radiator valves fixed?