From Lucky, it's about time
Anyway, in that last post reader Khan noted that British Airways has actually changed this policy as of last month, finally. Per this FlyerTalk post:
As part of a programme of changes for our Executive Club Members, we are delivering something that I know you will really welcome following a lot of your feedback on Flyertalk. From today, Executive Club Members can call any service centre to make or change their bookings. This includes both tickets booked with cash or with Avios. You will no longer be asked to call only your local service centre. The numbers that you call will not change and we do encourage to call your local service centre when you are in your country of Membership but we realise that there will be times when you need to reach us wherever you are and our colleagues will be happy to help.