[InsaneAK]

I normally just send my Nike FTID and Amazon FTID with empty Envelopes and an edited prepaid tracking label - worked for them so thought maybe could work for John Lewis

Yeah correct. Just put the edited shipping label onto a plain white envelope and sent it. Reckon it would work?

As in just sending back an empty box.
To clarify, you stuck the tracking label on an envelope for paper mail folded in half/thirds, or a bigger envelope that'll fit paper flat?

Can't really say. Can only hope for the best. I'm honestly leaning a bit towards no because I've never heard of an envelope (an empty one nonetheless) with a tracking label. Maybe I'm just uninformed though. Normally envelopes are sent with a stamp.  Keep us updated, I'm curious if it works.