Carrying any folder presents some challenge. Within what is possible Pakit was mentioned in this forum as easier to carry than other bikes. In the case of Brompton, you can make it maneuverable like a travel suitcase, with an addition of a couple of roller wheels directed to the side. The Sidewinder kit to accomplish this was offered on Ebay by a seller named doublesdave. While he has not posted that offer there recently, it might be possible to get such a kit by messaging him or one might turn to DIY as described here. Even a 6sp Brompton is insufficient for a surrounding with serious hills - more investment or DIY is needed in going beyond what is available as stock.