heating system in house

i am buying a semi three bed in dublin with a hot air heating system that blows hot air through vents into each room >
can anyone give me a ball park figure on what it would cost to put an oil or gas system in>
a very outside guess will do me >>>>thanks

Do you mean an apparatus that heats up the air to be blown in through the vents which should run on gas or oil? Or do you mean a central heating system delivering hot water for the radiators/UFH? A gas/oil fueled boiler?
There is a cheap combi condensing boiler available from B&Q, check the "good deals,bad deals" section here on AAM.