£15,000 for gas central heating or install Dimplex Quantum?

Robwiz

I wouldn't waste your money on installing gas.

Running costs per kWh using night storage heaters (NSH) can be in the same ballpark as gas - around 5p/kWh depending on supply companies' best tariffs. The Dimplex Quantums are Green Deal approved.

As an aside it may be worth getting an Energy Performance Certificate/Green Deal Assessment – the assessor would be able to tell you what effect the different heating options will have on your EPC rating – which is the most important consideration when you're thinking of selling your home.

An air source heat pump could be an option, however, siting the outdoor unit where it won't upset the neighbours could be challenging, particularly as the garden is shared. You'd need to be certain you contracted an installer who knows what he's doing as many do not and get the sizing wrong which is catastrophic.

A further alternative, not mentioned so far, is to install air to air heat pumps. Chosen carefully, based on heat output and coefficient of performance (effectively how much heat they put out per kWh of energy used), they can be cheaper than gas. An installer would advise you on layout, but one in your main living area and one on the corridor of the other two floors would be a good starting point.

If you go with NSH, I wouldn't bother with heating the corridors – leave a room door open instead.

In your situation, it looks as though biomass would be unsuitable due to your shortage of space for a big boiler, thermal store and wood/pellet store. Solar PV won't generate any electricity when you want to heat your house – most of your generation will be in the summer months when you won't need any heating. What solar PV does give you is an income that offsets your electricity costs.

Most landlords love electric heating due to low maintenance costs and the savings on gas safety inspections so electric heating isn't the curse it used to be.