Hmm I don’t even have a smoker...
What’s the cheapest smoker option if I wanted to do the oranges?
I did also consider really peat heavy whisky but might trouble the setting??
If you don't have a smoker/bbq then peaty whisky is a good shout. Just make the marmalade as normal and then when it's ready (and hot), whack in a reasonable dram or two. The alcohol evaporates immediately: careful for bubbling over.
It was a bit of a stab in the dark. Ice cubes in a shallow pan in a smoker for an hour seems to be the preferred option if you don't have fancy kit.
You could probably also just smoke the oranges whole, but the the water approach might be easier to control smokiness?