It looks like a nice conversion from the days when such updates were respected as sensible initiative rather than a compromise of originality.
When I first looked at it, I thought “Those are pre war BMW forks” and this impression was bolstered by the headlamp with what looks like a VDO speedo. In fact it looks like the complete front end with wheel, brake et al was just transplanted. As a practical matter this would make a very useable bike as the BMW forks were, I believe, well made and the brake would be a considerable improvement. I seem to remember that the BMW fork was copied in the UK after the war. Perhaps someone with a Sunbeam can enlighten us. A very useable and intersting bike that Titch Allen would approve of, if not the host of purists.