People have done the London to Brighton (~ 50 miles) on Bromptons, which have 16" wheels. Not sure I would want to do that, but I can certainly do 6 miles on my Brompton quite easily. And mine has only three gears, only two of which are really useful.
Actually, if you're really short on space,
Bromptons are truly amazing. Not cheap, but there's nothing to touch them for the way they fold up.