Having used them for many years I can say that Ergon GP2 Grips perfectly fit these needs and are extremely comfortable. The extensions allow a more extended position but also they are designed in such a way that the palm of your hand can rest naturally on the flattened surface and make for a much more comfortable ride overall.
On M-type Bromptons they need to be slightly trimmed as their length is excessive so just ask your Bike shop to do so when they fit them on the bike. They do not affect the fold of the bike and the handlebar is folded to its original position with the handlebar extensions only lightly resting on the floor.