ATMs - thanks for the info.
I assumed there was some logic like that, but was also wondering why we in the UK didn't go for the American method (was it simply that we weren't allowed to have 'G' all to ourselves).
Even with the current system, I was wondering whether the last two characters are random, or sequential. Using my example above, why is Luton EGGW not EGLU (which appears to be available).
NW3