The best price I can find for a 29HE and flue kit is from Discounted
Heating
(667+VAT), 'any suggestions for other suppliers?

They were the cheapest when I bought mine, too. IIRC, it was delivered from
PlumbCenter when it arrived, though. I think many of these Internet sites
are just excuses for the BMs to undercut themselves without having people
coming through the door demanding the "Internet" price. The same with QED-uk
and Miller Brothers.

Christian.