Not all canned vegetables have added salt. Most do, in America. There are then “low sodium” varieties of many of those. But very few come without any because you really need salt to bring the flavor out of some things.
What are some UK brands that you use? Just comparing some cut green beans from various places (as an aside: “mushy peas” is a thing in the UK?)
I’m looking at D’Aucy (French, I think) and they have 750mg of salt per 100g (a lot!!!). Del Monte (American) has 314mg per 100g. Sainsbury (UK, I think) has only 30mg/100g. Biona (UK?) is 290mg per 100g, Morrison’s (UK) trace amounts.
So the Sainsbury and Morrisons are definitely way lower than the other brands, but it appears to be specific brands.