I remember from working in a Brompton dealer for 3 years that there are so many little brompton bugs like that - the most recurring was the brake pad holders not being tightened properly, or even remotely in line with the rim!
Yeah out of the box, it's like that, but then again it is up to the reseller to ensure the bicycle is torqued and adjusted properly before selling them.
Swissstop BXP will work for you, don't go for that green stuff!
Hah, recurring problem when it haven't been torqued properly before it left the shop.