I'm not sure about this 'clean fuel' thing peddled by the gas retailers. I've had two houses with oil boilers and they run just as cleanly as gas when set correctly. Also with an oil boiler you can service it yourself, which like gas, is a very simple process that does not need a degree in rocket science and therforesave yourself a bundle of cash annually.
Comparing fuel costs in terms of Kilowatt hours. Electricity is 100% efficient at the point of use, I suspect solid fuel boilers are anything but? The other major drawback with a solid fuel boiler is the inconvenience and lack of flexibility. They could be great in a care home with a caretaker on duty to look after it and dispose of the ash etc etc but in a typical home with adults that work and a house that is uninhabited for large chunks of time then it's going to be wasteful. The furniture won't thank you for being warm.
Julian
Oil should be regulated like gas but won't be. You probably can service an oil boiler, wether you do it right is another thing.
Gassification is the way forward.