Hi either is Blue Anchor Farm and East Byshee Farm in Blindley Heath. They both have water complexes and are next to each other so can use both. Or there is Warren barn farm they have open days good complex usually done through the Warlingham horse club.
Failing that there is Ebbisham Farm Walton on the Hill or Pachesham Equestrian Centre leatherhead.
Don't think the water is very inviting at East Byshe...unless its changed since I last went there. I would say Tweseldown is worth the trip as it is very inviting and there are lots of different combinations with their water.
i like tweseldowns water although there aren't any tiny steps in, but lots of ramps in and nice sized steps. rogate in hants has a really nice baby water with ickle steps in.
the water at east byshee isnt particuarly inviting.
Warren barn has a v good watercomplex IMO. with about 5 or so different ways to jump in / through it etc. but for XC schooling its not as ideal as other places as the jumps are quite strung out.
If you want to see pics i have quite a few from doing the mock hunts there.