Hello Mike, Although the Brompton wheels are only 16" , OH says that she soon adapted to them, and with 6 gears it is fine for what she wanted. One of our main criteria was luggage space- and the Brompton when folded comes down to a package only slightly bigger than the wheel size, and that, along with its very light weight were two of the main deciding factors.We have to get it in the car, along with my electric mobility buggy and the rest of the usual caravan paraphanalia.
We find it fine on the Sustrans type of trails, going along at a steady 6 to 8 mph, to keep in step with my buggy,but as you mentioned, the saddle supplied was not the standard one!!( When I used to cycle, I always looked for a saddle that was as near to a tractor seat that I could find)