I always clarify before saying yes to their quote that the air fare is to be charged in GB£ by BA and the Propeller fee can be charged in whatever currency and by whichever merchant they want. Daniel is always very clear on responding to that.

As an O.T. the various Amex bonus offers of get 750/1500/3000 bonus avios, up to 3x, for spending £750/£1,500/£3,000 with BA/Avis/Marriott prior to 31 December are not triggered by spend with BA as billed by Propeller. They go through as “British Airways Atlas T London”, which do trigger 3x avios on a BAPP, but not the “spend £x to get x bonus avios”.