I'd get a Brooks C17 Carved in black, with black bartape:
10 year guarantee from Brooks, plus you can use it in the rain
I find this saddle more comfortable (especially on long rides) that a Gilles Berthoud Aravis or a Brooks B17
I do actually quite like this saddle, I've tried the non-carved one, and found it quite comfy, though not as much as my worn-in Aravis.
I've read it's very hard on clothes, though, so they wear out quickly - this problem is bad enough for me already with my GB Aravis, the crotch area in my jeans (which is what I wear for work, so commute in them) always wears out quite quickly, so if this is worse in that respect my clothes bill will cost me a fortune!
With my Brompton I will mostly be wearing "civilian" clothes, and even when I do wear cycling shorts (which I usually do if riding > 10 miles), I always wear light regular shorts or trousers on top.
Or do you find the wear on clothes is not a problem with this saddle and no worse than others?
Also am not sure a cut-out is needed with the quite upright riding position of Brompton M bars, so if I was to consider this, the regular version would probably be better.