Sandy,
Had another look at Post 5 on this thread, where you put that link to Wellingborough in 1803, showing who were the proprietors of the various Plots. Noticed that a David DULLY (sic), or even simply plain DULLY was also involved in Plots 96, 103, 197.
I've also read that (presumably this) David DULLY b.1773 d.1853 was one of "the early movers" in the Calvinist Baptist chapel, the Zoar Chapel in Zoar Yard which was built in 1808 but later demolished.
I also discovered from his 1853 will that one of his daughters, Ann, had married a man called Charles DRAWBRIDGE. This is the name of the minister of the High Street Particular Baptist Chapel in the 1851 religious census - it had an average congregation of 140, including the DULLEY's. No wonder there is such little evidence of the family in the Parish records. How often Nonconformist families successfully threw themselves into business, denied entry to other professions.
This is all getting very interesting...
keith