Hi Matt,
Sorry neede to be at home to view this and play.
I used another calculator, https://www.plumbnation.co.uk/heating-calculator/
Now I don’t know the make up of your house but based on mine but with your measurements I got larger heating requirements for lounge, bedrooms etc. Only the hall was similar. That not based on the cold winters of France but 50% on top of these ideals is where I would go. Interested to see how that works out?