Thanks for the replies folks, let me give you a tour of the living room ;-)
Here the "Chimney Breast" in question:
On the right of that is the inset gas boiler:
See insulation and attic space above, also missing insulation etc.
You can see the breezy electric heater I mentioned. It's not totally opened, there are some plasterboard internally but there's plenty of large holes punched through for cabling or possibly just the craic.
Here's a view from the recess of the electric heater, looking up (through one of the holes)
Same deal, gaps in insulation and no actual capping of the internal to prevent air movement.
Now you've got a better picture what do you think for this guys? For me I can easily hit the holes with expanding foam fill the air gaps around the plasterboard etc but sure it's still open at the top, I've practically got an exterior wall in the middle of the living room ;-)
Is that up to spec for 2005... or any year really, is it more an issue for the builder?