Fellow FlyerTalk member encountered DCC at an independent ATM near a supermarket in Inverness today. As with other ATMs, it was easy to opt-out, but the rate was awful:
MasterCard rate: 1 GBP = 1.245043 USD
Offered rate: 1 GBP = 1.3352 USD
DCC
markup: 8.855%

Amount
saved by opting out of DCC: $4.41