Just checked on Google/Plugshare. On the turn in to Bread and Meat Close. It looks like it not far from the main entrance on about 200 yds from the ticket office between 2 building on the left. (label over the first is Kumon Maths and English) 2nd building has a load of ,very wide, steps.
I wish the network operators would use 'what3words'. Would make our lives a lot easier.
Check Zap-Map and the comments left by other users. There’s a couple of photos of the actual location. Also only accessible when the Racecourse is open which seems to be Monday to Friday 8:30am to 4:30pm. Added to that, it appears not to be very reliable!