I too just got a 6 speed L Brompton ... have to say I'm finding the rolling when folded much better than I thought it would be. My experience is somewhat different than yours though, since my front wheel rolls nicely both forward and backwards. For the most part I push/pull flat and only lift onto the two small wheels when I need to turn. The one in critical thing that no one mentioned, was to make sure not to lower the seat post right to the ground, effectively putting on the brakes. Once I caught onto that, was pretty good rolling around.

That said, it's not much fun going over carpet or bumpy terrrain but the rolling of the front wheel seems to provide some stability as I use the bike as a shopping cart. I have thought about putting on easy wheels but am wondering if increased height will stop the front wheel from turning ...