I purchased some US Currency from Amex last week. I could not buy over £700 worth using my BA amex card. This was despite being able to buy more than this amount in May this year and having a £15000 limit.... I called Amex and they told me that the credit cards now have a £650 limit per day and using the card is treated as a cash withdrawal. As always Amex do not treat it as cash and I get the points and £650 towards my £10000 per year spend for the companion voucher. Very strange ....