Hello!
I just wanted to say that I'm really looking forward to seeing your layout as you build it - stumbled across the thread today. Your research is very good! The quarry at Purley was huge, and is now a large yard and sidings next to the station. Warren Road ran next to the station initially, but as the quarry got deeper they pushed the road back to where it is now, with the chalk 'cliff' to one side - hence the road above called Cliff End.
I was planning to make an N Gauge model of the line myself (as you stated earlier in the thread), but sadly I'm just too busy. Happy to help with any research that you may need - I have about 400 postcards/photo's/negatives of the railway.
Keep up the good work.
Chris.