From my days in the plumb center combi condensing boilers came in both flavours for town gas and LPG. So either way it would not normally be a problem, but have you considered replacement parts etc. and servicing. Unless you have a large gas reservoir, you'll be burning a bottle of gas a fortnight. A holiday home not too far away from us has a long rectangular electric water heater (not a ballon), which apart from being very efficient, is also reasonably cheap for the central heating. It would mean adding a water heater for general consumption, but an alternative. I won't go into my solar panel installation but needless to say it is paying its way.