Brompton

Nice one, I didn't know about that, I'll have a look for a second hand one to see if it would work, I suppose just a standard seatbag with a light attached would solve the problem as well...

The Moon front light will survive the fold and if you can fit the saddle rail mount for the rear on a Brompton, which I haven't tried, you could probably keep that on as well. If not, they both also come with silicone straps so they're really easy to take on and off.

From my experience of selling both, Exposure are really unreliable, while Comets can survive a full wash cycle.

I'd highly recommend Moon Comet front and rear, or a Moon Comet rear with a brighter front if you're doing a lot of riding in the dark.

That's what I've bought for my titanium Brompton project. Haven't fitted them yet properly, but a test fitting to the rat Brompton has proved that they'll work with the fold, and they're proper bright too.

Another vote for the moon, i got the small one on the front the gem I think which is USB chargeable, then the shield on the back which I stole of my larger moon set - also USB recharge.