i think id be able to fix that 1st time with out any parts and im SH*TE at fault finding ect.
as for the price, if he was right and got it up and running for christmas then you would you have been happy(ish)?
each manu claims a diff ammount so hard to tell, ans suppose theres a few factors to concider, efficiency of old rads, boiler type, room size, heat loss of room, which is something beyond my capabilities
more efficient, = less gas to heat the room(s) = less money to heat the room(s) which will bring energy bills down, which will complement the savings from the new boiler
imo much better off, new rads ''convect'' heat around the room. youl benefit much more. if you can afford it, and employ the right person you wont regret it.