Just my $0.02 worth:
(
Note: in the spirit of the discussion, perhaps I should write $A0.02 to avoid confusion with $US0.02, or maybe €0.02 as I live in Europe? - anyway, I digress...):
Due to the diversity of English I guess it's impossible to please everyone, so I would recommend the author write in the language and form with which they are comfortable. English is quite a hybrid language, except perhaps the US is more insulated from other variants than other countries - I suspect the UK has been infiltrated with more US usage than vice versa?
I have to admit in Australia I was taught UK spelling, so seeing US books when I was young took a bit of adjustment, but it was sort of 'Oh, OK' kind of thing, a shrug of the shoulder and move on - no major crisis, it was just how it was.
But a lot of the grammar taught to me, at least to do with punctuation, seems strictly more US than UK - I was taught to use double quotes, with singles as the secondary quote when needed, and I was also taugh that the closed quote always sits outside the full-stop (that's a 'period' to our US friends), comma, question mark, and so on - like thus: ("...end of sentence.").
As you may have noticed, I have taken a liking to the single quote, and tend to use that in my writing, as per the UK form, with double quotes as the secondary, thus: 'He claimed he had "never seen anything like it".' The UK usage seems to follow a contextual rule rather than a strict 'outside the other punctuation marks' rule, which I prefer.
Whilst having no major gripe with UK, US or any other English usage in particular, there are always some really annoying points with US spelling I find drive me nuts: lighted vs lit is one - 'he lighted a cigarette' or 'he lit a cigarette'. To me, 'lit' is the only choice, but I see more and more usage of lighted. There's a few other words like this.
Words ending in '-ise' or '-ize' still confuse me - it seems US is '-ize' but UK can use either '-ise' or '-ize'. I tend to use '-ise' but am not sure why - it just happens. I recall someone said to me that the '-ise' form was more prevalent in UK English because many of the words ending in '-ise' came from the French, which uses this form - not sure if that's crap or what.
I also always use centre instead of center, theatre instead of theater, defence instead of defense, and so on. I worked at a joint US/Australian defence facility some years back, and the name of the site was 'Joint Defence Facility' (as it was in Australia), but it was always a challenge to convince my US colleagues and visitors that it wasn't a spelling mistake?
Anyway, always lots of good items to discuss in usage of English language, and a chance for us to exchange ideas and expand our understanding. Cheers!
P.S. We don't have a strict grid system in Australia either, but regardless of whether streets run perpendicular or at angles and curves, a 'block' is usually clearly understood to mean 'a section of street from where one street crosses it to the next'. So this term was often used in suburbs as well as city centres, where you could say 'the shop is two blocks over' or something like that. I guess we probably had too much US TV!
