' Kersey Estate'. Does anybody know where this name comes from.

I assume it is the area that has brierson road backing onto riseldine down to holmesley?

Yes, the Kersey Estate is an estate developed between 1925-1930 by (renowned) architect A.H. Kersey. I believe the estate is boarded by Grierson road, Courtrai road, Honor Oak Park road and Stondon Park roads.