Ok , start here:
http://www.brompton.co.uk/, get back to me with some specific questions.
Gearing calculator here :
http://sheldonbrown.com/gears/internal.html
the new bikes have 2 different 3 speed hubs,
BSR is the continuation of the AW3 lineage.
have you heard of sturmey archer ?
BWR is a wider difference, between the gears, but the 2 cogs, 13/15t
[S=standard, W=wide]
do you understand ratios ? diameter and circumference?
are half step apart, and so the spacing between gear combinations, is tightened up .
the 2 speed is the 2 cog external gear shifter, and a 12/16t combination..
off the shelf, crank gear choices: 44, 50 and 54t
And the international currency exchange rates effect on prices?
sorry if I went over your head on the jargon,
been a bike mechanic for decades , ..these are
really basic concepts ..