what is it for matt
I hope Matt won't mind if I answer a question intended for him?
jags, there's a whole school of off-road touring called "bikepacking". See:
http://www.bikepacking.net/ It is more akin to backpacking than conventional touring. Rather than drawing on traditional touring practice and using a handlebar bag and 2-4 panniers, these folks prefer tying or strapping bags onto their bikes. It is an interesting approach. Besides flexibility in packing, putting the weight on/in the frame avoids the extra weight of racks and many feel it affects bike handling less. Without the constraint/weight of racks, it is possible to attach a lot of luggage pretty much anywhere on the bike using frame bags, saddle bags, and bags attached to the handlebars.
The bag Matt references is one of the latter. It is a "sausage roll" style with dual roll-closures. Helen attached it to her handlebars behind her conventional HB bag, as Matt mentioned. The purpose is to hold more stuff, in this case a bit closer to the steering axis so handling is less affected by the weight. These bags are a nice way to add extra carrying capacity beyond the conventional means even if one is not a "bikepacker".
Something along these lines might make it (more) possible to do some limited touring with your Raleigh until the Audax comes along.
Best,
Dan.