Think you got me confused with someone else I’m not up north (well north Norfolk), nor do I have a combi lol.
I do have a heatpump and very happy with it even with North facing, at the coast even during the coldest of weather we’ve faced in the past few years it keeps the house exactly where we want it and doesn’t break the bank doing so. How the installers left it setup was far from ideal so I have tinkered with it a lot heat curve and other settings plus dumping the anti legionella cycle.
All the best