Is the oil free/cheap? Even fair priced wood might be cheaper than oil.
An ordinary Oil Rayburn for cooking and hot water is not expensive to run,but if you are talking central heating,that`s when you burn big buck`s.
I have had an old oil converted solid fuel rayburn here at the farm for nearly 28yrs,it was here when i moved in,even when i was getting 8 ton of concessionary coal when i was still working underground,i found it cheap enough to run without converting it back to coal.
Reading the info on them Aga`s was like when i was researching about woodburners,i learned not to believe all i read,but at nearly 9 grand it must all be true,lol.