In an alternate history of the island that became modern Britain, prehistoric humans entered the Bronze Age but then (for various religious reasons - the full details of which are probably not pertinent to the question) decided it would be abhorrent to start dabbling with any other metals. Essentially, copper was deemed sacred while all other metals were considered profane and were banned (including in trade with mainland Europe). It is deemed acceptable to use a little tin to make bronze, but only where copper alone would be insufficient for a given purpose. Tribal leaders, nomads and even solitary hermits up and down the island share in these beliefs and enforce them as best they can. Even pure tin products themselves are prohibited; tin is only allowed to be used in the manufacture of bronze, making up no more than ~20% of the final alloy.
The ban is successfully upheld for thousands of years (aside from, one would assume, the odd smuggler dealing in small pieces of iron and steel contraband every so often) until the Roman occupation of Britain. At this point, groups of these bronze-loving people retreat into magically isolated parts of the country (in groups by the dozens or hundreds) to continue life without iron and other metals. The secret communities are able to easily trade and communicate with each other but remain undisturbed by the Romans and subsequent invaders. Put simply, they live and work in areas of Britain that are undiscoverable (not unlike a Harry Potter Fidelius charm or a Doctor Who perception filter), and they can source their copper, tin and other materials from these places in the same way as they normally would.
Presumably these constraints result in a ceiling effect as far as technological advancement is concerned, but how well could a bronze-based society actually develop before hitting their limits, if we allow them to freely use substitutes (copper, bronze containing only tin, or non-metals) where we would ordinarily use iron, steel, lead, brass, and any other metal or alloy? Specifically, could they make it as far as The Georgian/Victorian period? I should say, I don't need them to be able to harness electricity; they abhor that just as much as iron and steel
One thing to note: I'm happy to take a bit of creative license with geology here and state that availability is not a limiting factor. This is an Earth where copper and tin are as abundant as we need them to be to facilitate technological advancement. I'm more concerned with whether bronze's physical properties are actually fit for purpose. From what I've read, the reason prehistoric man graduated from bronze to iron was mostly down to the ease of sourcing and processing the latter, rather than the discovery of any superior physical properties (at the time, anyway). That answers my question for the first few hundred years of slow technological growth, but I'm wondering if a bronze-only society begins to fall down by the time we hit the middle ages or industrial revolution, where technology gets arguably more dependent on various alloys and their respective properties.
There are a few specific technologies I'm particularly unsure about, though I'm a new face here and perhaps it would be considered too broad to post a list of them. Perhaps not. I'll leave it here for the time being but happy to edit it out if it's not appropriate:
- Gaslamps (and, by extension, gas manufacture or natural gas extraction)
- Indoor plumbing
- Steam locomotives
- Early firearms
- A sewage system