I'd do the CH. The draughty windows could be improved for pennies as a
temporary measure.

Dave Plowman
Agreed, you can delay the windows for a few years. I used, as a temporary
measure the stick on plastic film which you contract by using a hair dryer,
it was very sucsessfull in cutting out draughts and reducing heat loss
considerably, it also lasted a couple of years so gave me the chance to save
some pennies towards the new windows.

Donwill