All electric heating of that type have the same running costs, given the same wattage - simplistically, you'll get one unit of heat out for every unit of electricity you feed it.
If the flat is insulated to the same standards as most 1980s properties you'll likely need to be spending a...
If the contractor has won the job having based his quote on those prices, tell him to use whoever gave him those prices - or at least ask him on what basis those prices have been calculated.
The reward doesn't have to be financial, am sure there'll be a local technical college that would welcome it as a donation - perhaps one of your elves could deliver it.
There's no physical address listed, no phone contact details - and the domain is registered to a private individual named Vasil Gyulev.
The company was formed a month ago, the registered address is:
KEMP HOUSE 160 CITY ROAD
LONDON
EC1V 2NX
Make of that what you will.
The instructions as posted very clearly make mention of CT and current transformer - so the first task will be to identify which set of terminals are for mains incoming, and which are for the CT.
The next task seems to be telling that POS what the CT ratio is.
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