I've just been chatting to a loft conversion company about loft
conversions and they seem to be of the opinion that I shouldn't try
and extend my open pumped CH system to the loft - but as far as I can
see all I need to do is raise the header tank to be above the loft
rads (all be it not by much) and it should just work.

Has anyone done this - does it work efficiently?

The builder seems to favour scrapping my perfectly functional boiler
and going for a new combi sealed system - which seems to me rather
over the top.

Thanks,

Ben