Ah... that explains why I got stuck at Motspur Park earlier...
17.24 Waterloo - Dorking charged through right on time.
17.30 Waterloo - Epsom was cancelled. 17.52 at Motspur - the one I was hoping to get!
17.39 Waterloo - Effingham, the 18.01 from Motspur, turned up 18 or 19 minutes late.
The screens were showing the 18.08 Chessington as being 12 minutes late and the 18.22 to Epsom ( 18.00 off Waterloo ) as being 8 minutes late.