Want to heat water only

[access]

I have an oil fired heating system that won't let me heat the water only.
If I want just hot water I have to turn down the thermostatic valves on each radiator in the house, the two rads in the hall and one in the bathroom have no thermostatic valves fitted so they stay on.
As you can see this is not an ideal set up when you only want hot water in the summer. My boiler is in my garage with two 28mm pipes going in to the house, I have been told that I could fit some sort of electronic valve to cure this but I don't know what type of valve to use or where it should be fitted.
If anyone can give me some advice on this it would be appreciated.

 

[ChrisR]

http://content.honeywell.com/uk/homes/Catalogue/Sundial Plans/3.4 Y Plan.pdf

 

[access]

Many thanks, that's just what I needed.

 

[ChrisR]

SHould ahve linked to here - see smartfit and S plan options too:
http://content.honeywell.com/uk/homes/catalogu.htm