Hi Stephen
It may help to know (if not now but later) that the Bax family seemed to have connections with the Quakers that worshiped in the Cuckfield/Slaugham area. I recall them as witnesses on a Quaker marriage in my own Betchley line. Unfortunately, the Quakers do not seem to have any records regarding baptisms, so you may draw a blank there, but the compensation is that their wills and declarations of, "Taking a Friend" in marriage, are usually very comprehensive, running into several pages. If you find one of these, you should be able to glean a lot about them, their lives, family and friends.
You may also find that although the Bax's were local to central Sussex, Quakers initially worshiped in secret and records from the 1700s that relate to events around Cuckfield are equally likely to be found just over the Surrey border in Capel. The 1732 Quaker marriage of Nathaniel Betchley to Sarah Steyning of Cuckfield for example, has numerous witnesses, including Phillip Bax, Richard Bax, Margaret Bax, Ann Bax, and Daniel Bax.
Roy G