My observation would be that due to the inherent distrust of both Governments and energy suppliers in the UK, most prospective customers will not be deterred by a fall in the comparative price of fuel oil. The CEO of BP stated yesterday in Davos that he expected the current situation to last for up to three years. We are talking about long term investment and also the motivation of having some independence in terms of energy production (which is what a heating system is).
When you look at the amortised costs of an installation, variance in the cost of fuel is only one element, and even halving it (which is unlikely to happen) may not mean the investment is not worthwhile. You can be sure that over the life of the equipment, the increase in cost of the displaced fuel will return to previous rates, as will the headline cost.
There are other variables we don't know. We could well see some form of carbon tax imposed whilst the price of fossil fuels are low, as its impact would be less felt. This would feed through to comparitive costs if there is inadequate decarbonisation of energy supply.
There is an argument that a changing energy mix may mean fossil fuel prices never recover as the marginal cost of other forms of energy become cheaper as we are seeing with both solar and wind.
Interuption to supply of some fossil fuels due to conflict could emerge quickly and unexpectedly.
I don't feel you have a lot to worry about from the price of oil. I would be more concerned about politicians or DECC tinkering with tariffs in response to any fall in the short term.
