I do have a relatively large area heated by the underfloor heating, but have set all thermostats to switch on only when required ie bedroom and bathroom in morning and living room and kitchen come on at 5-10pm.
Scottish Power did install a check meter for 2 weeks to confirm it wasn't a meter fault.
I've disconnected the thermostat in the living room as I had ruled out other rooms, and have noticed the meter slowing significantly since. Could it be a fault with the thermostat? If so, would I have any claim against the manufacturer/spark who installed it?
Thanks guys for all your comments and advice.