To muddy the waters even more i wouldnt be surprised and would expect a lot of countries including thr U.K to not accept entry to an a person entering from Thailand who has been vaccinated with a first dose of sinovac followed by a second dose of astra zeneca ( i have yet to hear of any other country in the world doing this ). I have no plans of visiting the U.K for a very long while yet but have already received my first sinovac dose ( i am grateful to get any vaccination offered here by the way ).