In article , Garry wrote:
Also are there any other factors which would make one a
better choice than the other?

I'd back up Andy's comments. I don't know about the W-B but two
useful (to some people) things about the Celsius are that you do
the air inlet and flue with cheap muPVC (not ordinary uPVC) 50mm
waste pipe rather than expensive flue extensions, and you can
remote wire the panel run/fail lights to another location if the
boiler is in an out-of-sight location

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Tony Bryer SDA UK 'Software to build on' http://www.sda.co.uk
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