Re: I seem to remember
I think the issue is that you may indeed heat your house with a GSHP (nice big garden?), but I bet you still have lights, washing machine, dishwasher, tumble-dryer, wifi, tv and a dozen other electronic gizmos plugged in or on charge. I would bet you travel to work in a car (or rail, bus) and fly abroad at least once a year. I imagine your house is relatively new to be efficiently heated by GSHP - so the materials are likely to have high carbon cost.
The cost of moving to renewables is not just magically switching on the GSHP we all have hiding in our gardens, but building them, delivering them, ensuring the housing stock is sufficiently energy efficient to use them. On top of that, some huge percentage of the population are not in locations where GSHPs can be installed. Even if they were, they would still commute, use modern tech and fly abroad on holiday. You can airily wave away the needs of the third world countries ("let them all use solar!"), but beyond nice, very low powered (and not very bright) LED lights, the moment they start pulling themselves up to a better standard of living, they'll need massively more energy too.
Your personal heating is a gnat's testicle compared to the steaming pile of energy we all use all the time. This is from someone who has a low energy home, heats it through solar and on-site biofuels (logs!) and has looked into the options for off-grid and renewables.