There are no facilities on Warren Farm, but the good news is that they are not far away!
Nonsuch Mansion House is only a five minute walk from Warren Farm, through Nonsuch Park. It has the Pantry Cafe and Loos.
The Loos are open 9:30 – 17:00 (or dusk if dusk comes sooner).
There is also a Toby Carvery on the corner of Cheam Road and Arundel Avenue. This is en route from Ewell East railway station and is about a ten minute walk away