To add some rise to an S type. Not 100% sure but don't think they needed new cables. They also upgraded the shifter to an SA one. It would be in this thread if you can be bothered to trawl.
18 miles a day on a Brompton, that's quite a lots for a Brompton. If it's still new. Perhaps talk to your shop about changing the handlebar for an M-Type.
I think I vaguely remember someone here using these https://www.sjscycles.co.uk/handlebars/thorn-mk2-comfort-handlebars-254mm-clamp-620mm-satin-black/
To add some rise to an S type. Not 100% sure but don't think they needed new cables. They also upgraded the shifter to an SA one. It would be in this thread if you can be bothered to trawl.