I'm looking for a reliable modulating condensing boiler (with
reasonable spares availability).

Can anyone kindly put the following list in a league table of quality
(ignore cost):

A. Viessmann Vitodens 300
B. Worcester Bosch Greenstar 28HE
C. Ferroli Maxima 35S
D. Keston Celsius C40
E. Vaillant Ecomax 635E

The table above (with the Vitodens, the best, at the top) is based on
my perusal of the threads in this newsgroup. I would appreciate an
update, however.