Pippy
I had a walk round Hylands a couple of years ago when visiting friends in Chelmsford and there must have been a car park because we drove there.The house is used for weddings and other functions so there must be car parking provided. If you are going to one of the pop concerts that are held there annually I would think that they will have special parking in one of the fields ( Hylands is situated pretty much in open countryside).
OH has just said that there was a free car park at both entrances.
I lived in Chelmsford for three years when I was first married a long long time ago. When I was young (and slim).