so how easy are these things to fit then? grin

It could be anything from extremely simple to very complicated, depending on
what you have installed.

The following information should help in determining what your current
system is. We already know it is a back boiler.

1. How many pipes come out of the boiler? How large are they?

2. Does your programmer allow you select the heating, but have the water
turned off, or are you forced to have the water on? (Or you can turn the hot
water off, but it has no effect, the hot water cylinder is heated anyway).

3. Can you hear/feel the pump operating when the heating is off, but the hot
water is turned on?

4. Are there any zone valves? These are large valve, that look like a
stopcock, except the handle has been replaced by a plastic box about 8cm x
8cm x 6cm which a flex trailing out. We need to know how many such valves
you can find, where they are installed, and how much pipes come out of them.

Christian.