Thanks for the reply. I have to admit that I preferred the upright position and lazy geometry more than I preferred the step through itself. I wasn't worried about going fast so the weight of the bike was probably advantageous as it steam-rollered over and through everything. The bikes I used in Helsinki were aluminium and seemed more than stiff enough (I weigh 105 kg). However the cycle paths in Helsinki were universally smooth which is not something that can be said of the roads and paths in the UK, so I may be better off looking at steel frames.