An advantage often touted about a folding bike is that you can take it into a restaurant with you or a movie theatre, shopping centre, out with your friends and so on. A brompton is the best for this kind of activity. You also don't have to rely on public transport but you can fold it of course if you like and hop on board. Counter argument: all that looks nice and pretty in the brochures with happy smiling people merrily taking their brompton up and down the stairs, a restaurant with nicely spaced out tables and not at all full, a little brompton perched up beside a rather happy and smiling person talking with their friends while eating some tasty food. The reality is a brompton weighs at least 10kg and often a lot more if you go for anything more than a single speed with fenders. Carrying such a thing is fine for a very short while, but can you imagine walking with your friends while carrying the bike, then to a restaurant or going out shopping while keeping an eye on your bike and carrying a bulky 10kg metal weight everywhere? That'll soon become a drag and you might even lose some friends (I'm not sure brompton riders actually have any but there you go - nerds). The alternative: I would say its far better to have a full size bike and if your journeys are less than an hour, just use something like a Triban 540 or some such machine and a couple of good locks. Hang on some fenders and I reckon it's a better proposition than a folder. Lock it up, out of the way, don't need to carry it. A couple of locks and there should be a reasonable expectation that it's still there when you get back. Maybe truck itnoit with tamper proof skewers and a cable lock thru the saddle rails and that should be fine. What do you reckon? (Talking of which, this particular nerd might want to get aforementioned cheap bike).