one thing i cant understand, is Baxi are the best!
i know of several warranty engineers flat out on repairs (in the 2 year warranty period) and i seem to spend a lot of time working on the older ones myself?!?
not saying they are a bad boiler, and as a seviceman i like to work on them, but IMHO i would have a Vaillant in my house
installation costs do vary, via, install issues, siting of condensates, and many other issues including boiler make, type, size, etc .......so hard to make a straight comparison unless given all the facts
as for flushing..YES YES YES YES YES,,,,and again YES....do it!
(all manufacturers insist on it and may void warranties if not done!)