My own house - 300L mains pressure hot water cylinder, Solar panels, radiator central heating, spa pool, homemade 3 way heat exchanger to transfer heat between the mains pressure potable water / closed circuit central heating water / spa water. And my main heat source is a home made waste oil fired boiler. It cost me a bit in both time and material costs to build it and install it. But running costs are almost nothing for almost unlimited mains pressure hot water, almost whole house heating. And the spa is more enjoyable knowing the electricity meter is madly spinning away to keep it hot. Currently only have radiators in the bedrooms. Will soon add radiators to the open plan lounge/kitchen/dining room and to the garage (because I can).
Alot of doing that is a hobby. But it helps that Im a Plumber / Gasfitter by trade.
Some useful info. What are you using for your main fuel? Diesel / bio diesel? What sort of water radiators do you have? Do you recommend heatpump water heaters as a way to heat the water for the radiators?