I'm guessing Sanday covers a wide geographical area so average line length could be an issue here. I see it has less than 200 residential and 15 non-res customers!
I didn't realise that the Scottish Exec funded exchanges were limited to 512. Is that all of them or just the really remote ones? Maybe they are reckoning that with such a small user base it would not be cost effective to do much more. You'll just need to compensate that with the fact you live in a great part of the country...and exchange contention is never going to be an issue is it