In fact the term oil filled radiator is a bit misleading, it convects heat more than radiates it. the term oil filled radiator is a misnomer.
Most things to do with heating are misnomers. Boilers don't boil (if they did the system could explode), as you correctly say radiators mostly convect rather than radiate. Copper pipes are in fact plain tube, not pipes (which have sockets and spigots) and header tanks are in fact cisterns not tanks (as they're open to atmospheric pressure).
Ah but the copper would be near the coal house. Actually, like the back boiler that replaced it, it is surprising how short the reign of the technology was, probably 70 years at the most. before that water would be heated in a container on the range. Equally, like the post war uptake of central heating, once a new idea comes along, it is pretty much standard after a few decades.
And most modern heating and plumbing engineers are in fact fitters of gas boilers, and stumped by anything more complex.
I always specify thermo-fluid types as they are low consumption/high performance with built in stat/timer as required. Can highly recommend these (Spanish Company but widely available in UK) http://www.farho.com/en/about-us/
