This has turned into a very interesting thread! I have collected some photos in an effort to create some sort of a "headlamp timeline":
Ram II with stirrup mounts and bucket headlamps on the three-piece final drive housing:
Sexton I with stirrup mounts and bucket headlamps on the three-piece final drive housing. Note the style of the guards.
Sexton II with stirrup mounts and bucket headlamps on the one-piece final drive housing. This one has the style of guards as on your
Shop No. 1164.
Sexton II with US socket headlamps mounted high up on the glacis plate:
As Adrian pointed out, the Butler/ Lucas headlamps with their mounting was a post-war British modification. As they do not look totally out of place and are part of this Sexton's history, you may well decide to keep them.