Thermaflow and air source heat pump

Looking at the thermaflow, it's Thermal Store - ie a highly insulated big hot water tank which heats the water up to a a very high temperature and your hot water and heating derive their heat via heat exchangers.

The tank will be heated by a combination of thermal solar panels, immersion heaters and possibly a heat pump. A heat pump wont be able to heat the tank above around 50 degrees, I'm not sure about the solar thermal, so it will need to be topped up with mains leccy, via the immersion heater hopefully during the off peak period.

As suggested, you do need to do some very careful sums to make sure that the system is set up to to provide enough heat storage to give you sufficient to heat the house and your hot water. You also need to look at the costs, solar thermal, thermal stores and heatpumps dont come cheap and you can't really rely on the sun to provide you wilth all your heating and hot water needs in the winter - possibly OK in the summer.

You'd need to save an awful lot of money to get a reasonable payback although you should get some RHI (Renewable Heat Incentive) payments to help offset the costs.

I would have thought that a straightforward heatpump system or even oil would work out a lot cheaper than adding the complexities of solar thermal.

Oil would probably be the cheapest to install, if you've got a space for the tank as you probably wont have to upgrade your heating system to cope with the lower flow temperatures of a heatpump.

It's a difficult decision and you need to understand the implications and cost of all scenarios - you need to talk to several different suppliers to get a better idea of what's available and what will suit your requirements and budget the best.