Hi Aage!
Another data point or two for your consideration...
I am of average dimensions and stand 180.3cm tall. I could have fit either a 565L or 590M Nomad and chose the 590M to use with drop handlebars. It fits well with a 60mm stem and compact drop handlebars -- to the millimeter the same as my other randonneur/touring bikes and I have found no handling problems with the longish Medium top tube and short stem. The bike also fits the same as my former (2011) Sherpa Mk2 in size 560S with a longer reach stem and longer reach/deeper drop handlebars. My Nomad's 590M frame would probably fit me equally well with straight handlebars and a longer reach (i.e. "more conventionally fitted") stem (I prefer a back angle of 45° when riding atop my brake hoods; same for on the handgrips of straight handlebars).
A couple more factors to keep in mind:
1) The weight-carrying capacity varies by frame size. This was also a consideration for me because while I don't always carry a lot of weight, I surely do load up on extended solo, self-supported expeditions in the back of beyond (especially so in the desert, when I must carry a lot of water -- up to ~26.5l/kg).
2) The top tube's actual slope will vary in steepness (degrees) by frame size as well, so if your standover clearance is marginal on one, it may be better on another. One factor for me in going for the larger frame is it helped put the handlebars up where I wanted them and there would be less exposed, unsupported seatpost than on the shorter frame (but enough to allow me to fit a Thuduster LT suspension seatpost, which proved to be very important to me). As it happens, the standover on the 590M is more than adequate for use on really rough logging roads and cross-country and has been most welcome as I would likely have bottomed out when stepping off the pedals onto a pothole if it had been any less. My other bikes with horizontal top tubes have sometimes been problematic in this regard, though never a problem on conventional pavement.
I'm in the field at the moment -- actually roadside astride the bike -- so don't have access to the charts in Thorn's Mega Brochure, but in the back of my mind, I seem to recall some possible variation in chainstay length between frame sizes as well. It might be worth checking if you have unusually large feet and need extra pannier/heel clearance, but it is unlikely you would have problems even then, as the Nomad has very long chainstays to ensure more of the load stays within the wheelbase.
As others have suggested, try asking Thorn again. In high season, they can get a little backed up and may have simply overlooked your initial email in the press of so many orders/support requests. I've found them to be extremely responsive on the second go -- with nice apologies, even! -- if they miss it on the first.
All the best,
Dan.