Martyndc88, not sure what you mean by turn on gas switch on boiler.
What I intend to do is:
Set all timer settings to OFF
Turn off gas at mains
On return:
Turn on gas at mains
Set HW to ON
Do I need to switch off the timer at the mains too??
There is no ON/OFF switch on the boiler, just the water temp. knob.
Just wanted to check that this procedure won't do any harm or cause problems when we get back.
Many thanks to all who have replied on here, by the way.