If you are buying a house with it then chances are there is no gas available so you're limited in choice- oil or electric. I have oil fired and it runs water and heating in a 4 bed victorian house (not really eco friendly), the oil comes in at £1000 a year and is cheaper than my last place which was pure electric. Don't go for a DD with one supplier as you are then tied to their price, shop around when you need to refuel and you'll get a good price.
Two things to look for when buying a house with it:
1) how old is the boiler, replacements run into the thousands so if it's really old take that off the offer price for the house and get it replace with a decent one
2) what type of tank is it, steel or bunded plastic. If it's steel then it is probably a single skin which means whenit rusts through it leaks. Again, take that off the price as you should replace it.
If you're worried about running dry then get an electronic monitor which will have a digital display in your house that warns you when you're running low. Or do what I do and check your tank once a week in the winter and once a monthin the summer. It's a bit like checking your car for petrol, you do that on a regular basis so you don't run out and it's not hard to do the same for your house fuel if you're organised.
Modern boilers shouldn't need resetting if you do run out as most will have a cut out and auto reset.