Teaching Grandmothers To Suck Eggs?

I do hope that I am not insulting the intelligence of my readers - you are on this Blog so there has to be a fair sparking of the old grey matter BUT  ....
Do all readers know that the one thing you must never do when exchanging currency is to do so on an airport? - It can cost you megabucks!

(I order mine online using a debit card, through ICE, Saga or The Post Office - whichever has the best rate -  and have it delivered to my door!)