I didn't know Campingaz had ever produced any threaded stove canisters
Campingaz canisters are
blue; no need to read any label.
EN417 is "Non-refillable metallic gas cartridges for liquefied petroleum gases, with or without a valve, for use with portable appliances. Construction, inspection, testing and marking"; nothing to do with the valve or threads. Pierceable canisters say EN417 on them too.
Propane/butane mix doesn't really work except in warm summer conditions, unless you are happy to buy the cartridges just for their propane content. Some stoves are designed to run on pure propane, although it is more expensive.
Stoves for pure propane are generally car camping stoves. There's no point in making light stoves as propane cylinders are necessarily heavy, so they are strong enough not to rupture in warm weather.
Smallish propane canisters are common in the US, but less so in the UK.
To get full use out of a propane/butane mix canister in
allmost conditions, you need a remote canister stove with preheat (MSR Windpro, Alpkit Koro etc), and to routinely use it with the canister upside down, even when fresh. Coleman propane/butane mix was fine in Scotland a month ago, 10-11° midday, 4° nighttime.