Where did the 240,000 BTU boiler come from? What size is your house? or
has
an extra nought crept in here?

To answer some confusion, the room stat etc would be on the boiler heating
system - not the Aga.

At present we have two 110,000 boilers on two separate heating circuits and
I want to rationalise with a single circuit and efficient modern boilers -
we have a rambling Victorian place with 28 radiators. Both installers I have
spoken to think we will need a boiler of up to 240,000 BTU capacity.

HTH