Duke wrote:
The building regs have something to say about where an flue for a
boiler can be positioned, in relation to windows, etc. Can the
relevant section be found online anywhere?

AFAIK it's not in the building regs as such; this comes under British
Standards which Ed Sirett has kindly (if a little dodgily! :-) ) made
available on his website at http://tinyurl.com/38ubcs (or
http://www.makewrite.demon.co.uk/GasFittingStandards/BS%205440-1%20-%202000.pdf

It's pretty turgid stuff though - you'd be better off consulting the
user-friendly version which will surely be included with your
installation instructions.

Actually, I don't want to position it anywhere near a window; I want
it to go straight out through a cavity brick wall, to appear about 8
ft above the public pavement outside. Is this acceptable?

Sounds fine in principle to me, but there might be other issues (eg
proximity to a boundary). And where does your pressure relief drain go?
That might be an issue 8' above the pavement!

David