I'm not sure that this applies in Ireland, but I will check up what I need to do here in terms of the regulations.
I've been doing a bit more investigation and it now looks relatively straight forward. Here's the plan:
I intend to install this in the fireplace:
http://www.esse.com/stoves/multifuel_wood/350gs.htmlAnd pipe it to the airing cupboard above where my two radiator circuits terminate. In the airing cupboard, I will install one of these:
http://www.esse.com/pdfs/Centraliser.pdfto "mix" heat from my existing oil boiler with the solid fuel heat.
My existing system is closed with a pressure vessel. The instructions say I need a header tank, but I don't understand why. Can't I just have a pressure blow-off valve piped to outside from the solid fuel burner?