The answer turned out to be not likely. But what is likely is that the characters would encounter several fat, rich, self-satisfied slave ships owners in the city and I can twist Big Traumatic Moment that way.
But as I read, I came across a mention of the Society of Merchant Venturers in Bristol. It started as a guild and ended up largely running the city of Bristol and its port for centuries. They had a huge economic impact in Bristol in that the Society argued against a London society that had a monopoly in the slave trade.
What I'm trying to figure out is if Miles, a merchant, a successful merchant who has just established a foothold in Bristol's busy port, actually needs to be a member of this society in order to run to his business. Did every prominent merchant who came to settle in Bristol have to be a member? Did they pay something to this society? If they weren't members, did that affect how much they could use the port?
If he doesn't, then Miles won't be a member--he's not a slave trader and doesn't appreciate those who are--but if he does, it adds another strand to his becoming acquainted and integrated into English rich-people society.