My husband and I were challenged at Paris airport about having only a Day 2 test booked for UK because UK didn't recognise the AstroZeneca vaccinations that we had done in Kenya. We were ordered to book a second Covid test if we wanted to get on the flight. I was able to book a Day 8 only test (sometimes only sold as a Day 2 & Day 8 package) through CityDoc in a few minutes using my iPhone, but the cost was £70 per person. When I arrived in London, I checked with immigration and they said I didn't need to have the Day 8 test as the AZ in Kenya was indeed recognised. I contacted CityDoc immediately and spoke to Alex who was very understanding and agreed to refund me the money as the Day 8 kits hadn't yet been despatched. They also do a package for Day 2 & Day 8 if that is what you need at a reduced price.