Seen a few on the Downs whilst out running. From memory, a couple near between Jack and Jill Windmills and the A27 (by the small clump of tall trees on top of the hill) , one down towards Falmer and a couple over near the Sustainability Centre (a few miles West of Butser Hill)
There are - go to somewhere like Hampton Court or Richmond Park and they are everywhere. We've got relatives who live near Surbiton and they have them on their bird feeders in the garden all the time. I played golf with my wife's uncle at Maldon Gc, loads there too...