as usual I cant find an Image I must have somewhere that (from memory...and you know what thats like) i looking into the garage from further away and you can see quite a few UK registered cars parked outside and I think the general consensus was that it was the back of the Peerless Garages/workshop prior to leaving for Le Mans.
I am not sure it is Slough. I can see UK registered car in the doorway. But the electric polls are not very UK. The big house behind is very french. Coble street not very Slough trading estate. Posters on walls not UK brands. Would more like Lucas and champion. Love to know though either way. Great images amazing to see both cars