Just one other bit of information, not sure if it helps or not, but the Remeha is currently supplying (in the main house) 28 radiators of various sizes and underfloor heating in the conservatory which is 10m by 4m.
The other idea of using the Remeha from the main house with this PEX twin pipe is very interesting as we know this boiler has the capacity and therefore I am guessing the additional running costs will be minimal and we then eliminate our meter problem.
I will investigate!
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