Hi Dick
I emailed you a couple of photos. The sunroof on the Slough cars was an optional extra. I would have thought all Slough cars had leather seats apart from the popular model produced shortly after the war which was based on the Paris build. Central air vent on the scuttle is standard. Above the windscreen I wonder if that is an old fixing for a sunvisor as Larry mentioned. Whether they were used as Taxis is an open question, probably not from new.
Can you put up a picture of your car’s interior?
Patrick