Found more on the message:
http://www.headforpoints.com/2015/01...ith-amex-gold/
Back in December 2013 I wrote a piece entitled ‘When is £ credit card spend treated as foreign spend?‘. The list of companies who processed your £ transactions outside the UK, thus triggering double points on the Amex Gold card, included Apple, iTunes, Amazon, easyJet, hotels.com, ebookers, American Airlines, Hotelopia, lastminute.com, Ocado and Paypal.
Information regarding additional Membership Rewards® points earned for spend at non-UK merchants
It has come to our attention that you may have previously earned additional Membership Rewards points where a transaction was charged and billed in pound Sterling at non-UK merchants, although such transactions do not attract a bonus under the Membership Rewards programme linked to your Card.
From 21 March 2015, transactions charged and billed in pound Sterling at non-UK merchants will no longer attract 1 additional Membership Rewards point for every equivalent £1 spent. This includes transactions that are converted into pound Sterling by the merchant before being charged and billed (known as “dynamic currency conversion”). Please note that we will not remove any additional Membership Rewards points that have been awarded to you for such transactions up to and including 20 March 2015.
You are (and will remain) eligible to earn an additional 1 Membership Rewards point for every equivalent £1 spent on non-Sterling transactions. If your transaction is converted into pound Sterling before submitting to us, you will earn at your normal rate. Transactions charged and billed in pound Sterling at merchants registered outside of the UK do not attract 1 additional Membership Rewards point for every equivalent £1 spent.
This sounds more like multi-currency processing rather than DCC on V/M as we know it. Probably still a false alarm. Amex UK has just joined Citi HK in mislabelling a foreign transaction/cross-border transaction as DCC.