Cost will always be an issue with any new tech, not just the affordability but also human spending habit.Bet it will take u 10 years to break even though.. Maybe longer.
Solar panels last I checked ain't cheap to install and is quite expensive.
Materials for it is expensive and the labour plus scaffolding is also not cheap.
Did you already have insulated walls? Roof and ground floor insulation?
Did you also already have suitable radiator sizes and also a place to store the hot water cylinder tank?
No one ever talk about ROI of buying a Car, Jacket, Watch, food. but when it comes to Solar and renewable then how many years before it will break even.... If you have an existing working system then don't do anything and you will have 100% ROI in zero year
I did my solar and battery install myself and got an electrician to wire the final part, apply for DNO myself and that save a lot of money. My calculation was ROI of 8-12 years but with the unexpected price hike it is now a lot less and that alone was not the decision for me going down that route.
With the Governments grant of 5k towards ASHP it is like free money (not free as it is paid by taxes collected) but like company contribution to pension if you put in £10 and they match £10 then it is £1o of free money which other wise "lost"
What we really needs is a ASHP which works at higher temperature like the gas boiler, doesn't need high flow rate and can be use replace gas boiler without any mods and still have the 400% efficiency.......not too much to ask for in 2023. Just get the AI to do some work for a few minutes.