I don't think they make a "Vitesse D7" anymore, so if a local shop has one, it's an older model. So old, in fact, that some of its parts may already be obsolete.

The latest Vitesse models have internal hubs, which are a little less efficient than derailleurs, but a little more reliable and better for wet weather.

The Dahons are just about small enough to put under your desk and ought to be fine for what you're doing. Another option is the Brompton, which has the smallest/best fold and are super-convenient, but are a little more expensive than the Dahons.