2) we live 200m from the fylde coast and speaking to neighbours around here, they have had big issues with salt corrosion and sand egress into their heat pumps.

Are your neighbours units specifically designed for coastal areas and are your neighbours regularly rinsing off the unit and its heat exchanger?

In the Findhorn eco village, which is bounded by dunes and close to the Moray Firth, the heatpumps are almost exclusively Mitsubishi Ecodan units which I'm guessing will be the coastal variant.

Would ground source be an option for you? As that would eliminate the external unit.

As I said earlier, I have just removed my storage heaters, two of which were newer dimplex quantum. Resistive heating was expensive to run and the house was only partly heated to a comfortable temperature.... A battery / solar install to cover the heating demands were completely unrealistic. I haven't removed the infrared panels, as they don't interfere with anything and they may be required on very cold days.

Unless your heat demand is ONLY 1kw, your battery isn't going to last the day feeding an electric heater.

Occurs to me you might want to look at the videos by Andrew Till / Mr EV on youtube. He went with the electric heaters but lots of solar/battery choice.

Makes me wonder though, if an HP uses less energy than it generates, what the issues with it having generate electricity instead of hot water, or is the water it heats for the radiators not hot enough to generate electricity?

That's because it doesn't generate electricity. In fact, it doesn't generate energy at all. All it does is move heat from one place to another, and that process is efficient enough that the energy it needs to do the moving is significantly less than the amount of energy it moves.

You already have a heat pump in your house, so you can see the physics in action. The inside of your fridge is cold, but the coil at the back of it is warm. The fridge isn't cooling per se; it's just moving heat energy from inside to outside and heating your house in the process. Similarly, my heat pump in winter is expending a lot of energy trying to cool Surrey down further, and the heat it removes from the Surrey countryside is dumped into my house. There is a very good introduction to the whole topic at https://renewableheatinghub.co.uk/heat-pump-basics-jargon-free-guide/

A heat pump moves energy from A to B efficiently, especially if the differentials are low. Trying to generate electricity from heat is very different and needs high temperatures to achieve even 30-40% efficiency. Physics doesn't let you print free money.

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we live 200m from the fylde coast and speaking to neighbours around here, they have had big issues with salt corrosion and sand egress into their heat pumps. 1 person even went so far as to install the heat pump in his not-used garage with some vents for air in/out but he had only just done that and I don't have that much spare space.

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One thing that strikes me is that unless you have an unusually high density of installed heat pumps around you, talking with the neighbours still only means canvassing a small number of opinions that could be thought of as "informed". If it's only two or three, that's easily few enough opinions to be influenced by other factors (such as bad or mediocre installers).

I absolutely agree with your approach of asking people who already have heat pumps, but you might want to get onto the Visit a Heat Pump web site and see if you can't meet up with a few more people with heat pumps who can give their opinions to add to your information gathering. At worst, you end up wasting a few trips out and get to the same conclusion. At best, you may find a heat pump is a reasonable alternative after all, and just possibly you might even get some tips on how to get a heat pump installed in such a way as to avoid sand ingress and salt corrosion.

I should also point out that we have an awful lot of coastline in the UK and there are a lot of heat pumps installed in that environment - even amongst this forum's members. I cannot believe yours is a situation that hasn't been addressed before, so the information's out there.

That aside from the water perspective the two are pretty much independent in the non air/water case. There is kit that does both but it's pretty leading edge. We actually went for the complete other end of the spectrum. Our water usage isn't particularly high so the heating went air/air but most of the water is heated by a good old fashioned immersion over night and we sometimes dump some solar into it if the batteries fill. In that case because of overnight low tariffs the heatpump payback was not good enough. If the day/night prices begin to get less polarised then I suspect we'll eventually have to revisit that choice.

There are Sunamp systems for heat pumps but require High Temperature pumps and we did not wish to fit an HT heat pump; hence our choice of the solar / grid powered version (Epv type). Some readers have written about the cost of such a system and others have mentioned the greater efficiency obtained when using ~350% or higher COP of heat pumps but, space did not permit a large tank and we do have solar power which powers the system for a fair proportion of the year. We didn’t have the space and Sunamp is a solution! Regards, Toodles.