BA Holidays must originate in the UK to qualify for double tier points.
Holidays Double Tier Points | British Airways
A “Qualifying Booking” is a British Airways Holidays booking that meets all of the following criteria:
a. The booking must be for a British Airways Holidays Flights + Hotel or Flights + Car or Flights + Hotel + Car package booking originating in the UK only and the hotel or car element of the booking must be booked for the duration of the trip.
b. British Airways flights including codeshares and British Airways marketed and/or operated flights only.
c. The booking must be made before 22 October 2022.
d. Travel is for outbound departures between 9 June 2021 and 31 October 2022 inclusive (final outbound departure date is 31 October 2022).
e. The booking must be for a stay of 5 nights or more.
f. For departures prior to 24 August 2021, the booking must be for a minimum of 2 passengers. From 24 August 2021, there is no minimum number of passengers required.
g. The participant must register their Executive Club number against their booking prior to travel.