For a slightly more costly but more alternatives & flash & dual fixed/flash option, I would recommend the Cateye Volt 50. Excellent and very bright light.
It comes with a saddle rail mount, albeit I found this rather flimsy and barely fit for purpose.
For a couple of quid you can get a seatpost band mount that is far better and will sit high enough up that it doesn't interfere with the fold at all.
USB charging, excellent battery life and a very robust weather proof light. Compact enough to fit unobtrusively in a pocket off the bike & with enough weight to sit there without jiggling out. Again highly recommended. Can be an only light but I use this and the Trelock together (I never have just one light on a bike)