Bought some stuff on eBay in GBP with a USD credit card. Used the "credit card" option implemented by Paypal which doesn't disclose DCC but does it anyway. Wrote a message to Paypal asking them to represent in GBP, credit the difference (about $1), or threatening to chargeback. They credited the difference to my account.
Now know to use the "Paypal" option (depsite both being implemented by Paypal) and log into my account which does have the option to evade DCC.