Wow, welcome to the bikepacking community.
Prepare to be overwhelmed by all of the bikes on the market. First you don't need female specific but if you find one to make comparisons to that would be good. Gears are your friend, people ride single speed bikes but unless your super strong or want to get that way gears are nice to have. There's nothing wrong with the 9 speed stuff but most higher end bikes will likely be 2x10 or 1x11. People are completing big rides on the new skinny chains of the 1x11 so my skepticism may be unfounded. Carbon is nice if you can afford it, but plenty of people ride steel hardtails and most full suspension bikes come in aluminum first and carbon as an upgrade. Good luck finding a MTB with rim brakes I haven't seen one lately, plus you want disc. The Shimano XT is considered a workhorse and I've seen them recommended by a major record holder here. Rims not sure if Stan's
http://www.notubes.com/ are available in the UK but they are the standard tubeless set up here in the states. You want tubeless or tubeless ready.
Ect ect, if you do a bunch of research look up some of the personal setups
http://www.bikepacking.net/category/individual_setups/ to get some ideas. What you want is a Cross Country mountain bike. But make sure to let them know you plan on touring/bikepacking and that you need durability as well. You should be able to as you say get it right the first time.
It's good that you know something about bikes to start with, understanding the different levels of components should come easier for you. Like with road bikes the more you spend the better quality you get, but you also need durability so you don't want or need the lightest race stuff. In the Shimano branded stuff I would say you want XT not XTR the r for race is a lighter version great for short track not for the long haul. Sram is the other big name in components for MTB at least here in the states, they have a similar upper race level and then the next step down is likely the more durable version.
So I hope that helps get you started.
I don't see GDMBR on the calender
http://www.bikepacking.net/forum/index.php?topic=11039.0 I think the GCMBR the one that started at the Canadian border has been replaced by Tour Divide or TD for short and starts in Banff, Canada now. TD is sometimes considered to be a dirt road ride rather then a true MTB ride. So yes some riders attach clip on TT bars
http://www.backcountry.com/profile-design-t4-clip-on-tt-bar?CMP_SKU=PRD0019&MER=0406&skid=PRD0019-ONECOL-ONESIZ&CMP_ID=SH_SHP001&mv_pc=r110&003=7163546&010=PRD0019-ONECOL-ONESIZ&utm_source=Shopping_com&utm_medium=CSE&mr:referralID=1d59ffc1-b16b-11e4-82f7-001b2166c2c0 These would only work for a route like the TD, not sure exactly what trans-alp has for tech but I think it's more of a trail ride with more technical terrain. Can't see having them on single track trails.
Jax my name is Tim AKA the Arizona Trail Tripper I guess folk on the AZT race threads call me the helpful guy. Having been lucky enough to get to ride the whole thing twice I like to help others get out and experience the trail.
Tim
