Face/head transplants rarely work.
See Hayden's creepy Force Ghost for proof.
I've seen your avatar image elsewhere but I can't seem to find a larger version of it.
The real trick is finding two sources which match in lighting and position, the PT has a lot of shots of Ewan's Obi-Wan but finding a matching (even near matching) photograph of Sir Alec of the right period that ticks all the boxes while possible would be very difficult.