Hello Shaun and thank you for your interest in my greatx2 grandfather's brother. I've followed your two links to Find my Past, it's interesting that the two tailors mentioned are both in the "Northern Parts". You imply that you have seen other other occurrences of the phrase "Borough Tailor", were they also from a long way away from Cornwall? I ask because there is no sign of the Oldham family in Cornwall before Charles Oldham (Thomas' father) married Prudence Davies in December 1789. Several official documents suggest that Charles was born c 1765 and an elderly member of my extended family believed that he was born in Oldham. If that is true then possibly it was Charles who introduced the phrase into Cornwall.
About a year ago a cousin acquired, at auction a brass nameplate bearing the name
OLDHAM TAILOR. Expert opinion is that the nameplate dates from the 1820's but the auctioneer had no idea where it had been since then. We then discovered that the name plate had been sold a couple of years previously, with the auction catalogue stating that it had been the property of John Oldham of Padstow. That is incorrect as John (Thomas' younger brother) settled in Portreath following his marriage to Mary Ann Box in 1821 and didn't return to Padstow until the 1840's. We suspect that the nameplate belonged to Thomas, about whom we know very little.
I am at a loss to know where to look next, I wonder if trade directories might give a clue.
Apologies for being slow to respond but I didn't get an e/mail telling me of your post, for which renewed thanks!