Many thanks for the extra information, Sean . . . it's always good to add a few more details to the record.
Andrea, I'm afraid the Slaugham connection came from a submitted record on the IGI via someone else's tree, so it may well be wrong. Thomas' family was the subject of a Settlement Certificate issued at Pulborough in 1792, the foreign parish being Ockley, Surrey. I thought he might have been born in Pulborough but there don't seem to be any Stone baptisms there before the 1790s, on the IGI. There were plenty at Ockley, back to the 1500s, but he doesn't seem to be there either.
The Thomas baptized on 5 May 1771 at Slaugham had parents named Thomas & Sarah, the same names as Thomas' & Ann's first two children . . . not uncommon names, but quite a coincidence

Thanks for your help.
Mike.