Electric combi boilers / solar panels / eco heating solutions

I guess it depends how much electricity you use.

We're around 900 kWh to 1 mWh per month (including two electric cars).
That will go up to around 1.1-1.2 mWh per month when the heatpump is installed.

We use around 650 kWh per month for the EVs which is charged at 7.5p on Intelligent Octopus Go (11.30pm - 5.30am) and is renewable energy which is nice. The remainder is largely used during daylight hours for home working, watching TV, cooking (induction / electric oven). So this is around 11kWh per day. With a 9.6 kWh battery (charged at the 7.5p rate) we can basically run the house at zero cost without solar.

The benefit to solar is twofold - one, in the summer, there will be plenty to both top up the batter and run the house.
Two, we can export at 15p per kWh. This means that we should either be at zero cost or negative for the majority of our heating, cooking, driving, working etc etc.

The total cost of the heatpump, solar & battery is around £15k.

If we use historical costs for the house of around £3.5k per year for gas & electricity, then payback is only 4.2 years. Moving forwards beyond that timeline, it'll be a saving.

Obviously that's perfect scenario but in your situation, a battery and solar could zero out your energy bill and provide payback in a similar time period depending on usage.

Best thing to do is understand your current usage and spec a system that would be net zero or positive return and they calculate payback time. If it's under 10 years then it's probably worth it.