Well, you have to keep in mind that I live in Croatia:-) All non-Croat Alexandras I've met were Alex and in Croatia the nicknames for Aleksandra/Aleksandar are Sandi (m), Aleks (m), Aco (m) (pr. Ah-tzo), Sasha (m&f), Aleksa (f). I guess that in UK/US Lexie might be more dominant.