We have Dr Ho folding bikes, 27 gears. Was worried about carrying extra weight at back of caravan so opted for folders stored in large plastic storage containers (sans lids) in the back of the Jeep, thus carrying the weight in the middle of the rig. The very best brand are Brompton but way out of our price range. We got these for less than half price (approx $600) from Pushy's in Canberra. I believe they do sell on line.
My favourite is an original Aldi one, I have a repco as well. There are cheapies around the $200, and there are a heap of more expensive ones, I don't how much better they are because I haven't had a ride on more expensive ones. Mine is great to have with me, have shopped on it, doubled the dog on my lap.