Hi Paul,
Welcome to the Field search. You have got as far back as I have, Joseph Field (b 1740). It would be great to go back further but I have the inconvenience of a full time job which just seems to take up all my time unfortunately

My link to you is William Field (b 1880) who is the father to my great grandfather Clarence (b 1854) He went on to have 9 children (7 surviving), one being my grandfather Ernest.
I am friends with another distant relation who I met through an RAF kids page on FaceBook. Her mothers name was the same as ours and they had also been to the same overseas postings as us. She mentioned that her family orginated from Ticehurst and that is where we made the connection. Her great grandfather is Jacob Field (b 1844) another son of William.
Please keep us updated if you manage to get any further than 1740. One day I will find the time!
Kind regards
Sallie