Good idea...IF , as you say, they still process at the London embassy. It saves doing a years 'Probationary' 13A (in the Phils) before getting the full one (which I do have).
I know they stopped during Covid. Possible UK police report needed ? In the Phils once you've been there 6 months, and applying for 13A, only a cheap and quick NBI clearance needed.
Merry Christmas and a Happy New Year to you and yours Fred.