Thanks John. At the moment I've just switched the underfloor heating off by switching off the controllers in each room and ensuring the actuators are closed. When the DHW is switched off I have only changed the mode on the control panel to off instead of in the auto position which manages the DHW on a schedule. I do have the red tank you mention and there is a large blue lever on the cold water mains to the cylinder. I'll try to do what you have suggested and I am now going to also take meter readings every hour, record exactly what we used and then see if the meter readings tally with the actual usage.
Thanks,
Chris
Thanks,
Chris