Please note that I have now
found stumbled across the William Tibbel/Theobald ancestor in one of the last places I expected to find him, Chelmsford. He was baptised William Tibbles at Chelmsford in 1776, his parents were John Tibbles and Elizabeth French who married 1774 in Chelmsford.
So now the search begins again and yes I have searched Chelmsford

, also Moulsham St John and Springfield.
If anyone has a spare Elizabeth French (c1753) or a John Tibbles (c1749), any name variation acceptable, I'd be pleased to hear of them.
Thanks Clincher and Malcolm for your efforts to help.