The in house octopus heat pump is not one of the more efficient ones on the market and it's way behind the best ones from colder countries, why does that matter, because the more inefficient the more electric it's going to use.
They do have sensible survey and installation is usually ok but you may want to look at which pump they are wanting to install, the in-house one they make is what they will push but your paying the electricity bill, look at the scop and SPF. Look at valiant or nibe s2125 scop and weep the nibe will laugh at our winters where as you will be able to stand next to your octopus heat pump and keep warm from all the electricity it's using
It's not worth it for us as our combined electric and gas is just over 1k a year, would never make it back, our heating is usually on for a couple of hours then it's off, can't do that with a heat pump you have to know how cold your going to be tmrw
Solar and batteries help, just spend another 10k, you should break even some time about 2099 as long as electric don't go up, which it will.