I have been using a pair of Continental tyres on my Titanium Orange Brompton for some time now, cycling a good few hundred miles on them. I recently bought another pair and will fit them to my Orange Black Special Edition soon.
Previously I have used the standard Marathon tyre by Schwalbe and do think that they are pretty good. I have never got on with the Marathon Plus version, although some swear by them. These Continental tyres roll really well and noticeably lighter. I have cycled on some truly horrid London roads, cycle paths and also lots well away from London and been very happy with them.
If you are soon to replace your tyres you might want to give them a go as I know a few fellow Brompton riders who have converted.
A friend who lives in Calgary, Canada previously only had Kojak tyres on his Brompton but even he swears by these Continentals.
Stay safe out there people.