Thanks for your suggestions, chagzuki and Lalato. All reports I'v ever read say that the cost/benefit of ti parts is rather limited (you don't get a lot of weight reduction and it costs a lot), but it is something to think about. Lalato - yes, what I remember about the Tikit is how unwieldy I found balancing it while rolling it - a big difference between that and my Brompton which I can literally push across a room and let it roll by itself. The rear rack with rollerskate wheel to improve the Tikit's rolling looks interesting. I shirk at the cost, but then my Brompton rack cost me about the same. A Tikit with about 10 gears and a rear rack with the rollerskate wheel could be a good option - I'll investigate further. In the meantime, I have renewed respect for my Brompton!