Hi

thanks for your prompt reply.

The separate immersion heater should be set to off - it's only really a
backup in case the boiler fails.

OK - so do you mean OFF as in powered off OR use the over-ride switch
(which is a button on the immersion heater timer with a a icon of a
hand) to set it to OFF (which it says is OFF when a [O] icon is on
display) ?

The boiler programmer should have settings for heating and hot water. Are
you sure the heating one is on? What make is it?

the boiler program has 3 settings that i slide to set:

CONSTANT (or something like that) --- OFF --- TIMER

I have it set to CONSTANT

It then has 3 icons underneath it - one for central heating only
(because it looks like radiator), second one for both HW and CH, third
for HW only.

I have it on BOTH CH and HW.

So Heating one is on. the make I'm not sure - something like suvic? i
will check and post tomorrow.

what is strange is - if i set the boiler programmer to HW only, the
boiler comes on, if i set it to CH and HW both, the boiler comes on,
but if i set it to HW only, the boiler doesnt do anything.

that does that mean it thinks the temperature settings is too low? i
have set every single themorstat in the house to the MAX temperature
settins (room thermostat, hot water tank/cylinder thermostat)

there is also a clock on the boiler programmer and a knob that i can
turn which changes a little icon next to it to red or not red - this is
for the on/off when the program is in timer setting it seems.

thanks
Kiichi