I think you're confusing "have listened to a lot of..." with "have voices of a similar age to...", and especially in Jim's case even that isn't true. In fact they have all been listening a lot to much older singers than that, and I think that shows.

I don't think an attempt to clone YT or MacColl would be very imaginative. Their harmonies and arrangement aren't like anyone else's. Methinks you've set yourself up for disappointment by having too many (and too specific) expectations.

Anahata