Hi. I don't think I saw this query when it was posted - only saw it now when I was replying to another old post that had been resurrected.
You may well have the right Susannah - and there is a connection to Bristol. I have the following (not looked at this for ages)
28/3/1768 Humphrey Walloxall, parents Thomas and Mary, baptised Ribbesford (died young?)
7/4/1770 John Walloxall, parents Thomas and Mary, baptised Ribbesford
30/8/1772 Sarah Wolloxall, parents Thomas and Mary, baptised Ribbesford
14/2/1776 Thomas Walloxall, parents Thomas and Mary, baptised Ribbesford
3/11/1778 Susanna Wolloxall, parents Thomas and Mary, baptised Ribbesford
31/10/1780 Henry Wolloxall, parents Thomas and Mary, baptised Ribbesford
19/2/1785 William Wolloxall, parents Thomas and Mary, baptised Ribbesford
11/3/1787 Humphrey Wolloxall, parents Thomas and Mary, baptised Ribbesford
Humphrey is my 4xgrandfather and I have more on him, plus some details on some of the others. Thomas pops up in connection with Bristol I think, listed as subscriber to a poetry book published in 1799 "Mr Tho. Wolloxall of Bristol." He seems to have been over in Wales too, with his children registered at the Baptist Chapel, Caerleon, Newport, Wales in 1801/04/07. Humphrey was a waterman and I think Thomas was linked to the water/harbour in some way - there may be a thread on here about it.