Thank you Dave. I knew it was a big ask.
The system has, I believe 2 'barrel' fuses.
I believe the new heaters are, upstairs, 1kw equivalent 2.2kw (the old ones were Creda TSR12A 1.68 kw input rating and downstairs new ones 1.5kw equivalent 3.4kw (the old ones which were Dimplex XT24 and they...