Billingham bags are excellent quality and very expensive in the USA. They're less expensive in the UK, although still not cheap. I've bought them at some savings by ordering through Robert White Limited in the UK. (B&H sells the Hadley Pro at $293, Robert White's price for the same bag is $211; add shipping and you still save $50-60.)
I have had both the L2 "Alice" and the Hadley Pro. The L2 is about my favorite small SLR bag, works fine for a Leica M kit too but is deep enough to fit an SLR more comfortably than the Hadley Pro. I use it still. The Hadley Pro is a very nice bag indeed but I found it to be a bit more bulky than I wanted and seemed lacking in space for its size. I sold mine after a year and some and replaced it with the "Black Label Bag Oskar's One Day Bag II" from Photo Village in New York (a lookalike to the A&A ACAM 7100 but with a couple of small improvements, and hand-made in the USA). The Billingham is a little bit better made, maybe a little more weatherproof, but the BLB is trimmer, holds more, and is more functional.
The BLB has become my favorite bag when carrying more than just camera and one or two lenses. On my trip to the UK last Fall, it held a three lens Ricoh GXR-M kit plus iPad and all the accessories I needed with room to spare ... would do the same with Leica Ms. It runs about $200 or so. Here's a link if you care to look at it:
The only negative I've found is that the strap loop hardware attaching the shoulder strap to the bag was of poor quality. I removed the original loops and fitted a pair of West Marine stainless steel carabiners as replacement ... now the bag is as close to perfect as I need.