Have been really interested in Bell tents for a couple of years now for family car camping as I hate flappy nylon tents so have just got back from a week's camping in a 5m bell tent (hired) in sussex. We used a 5m, which was voluminous, to say the least... and really was much more than we needed for sleeping space for two adults and two kids. It was easy to heat with a small stove and a few hundred grams of dry wood. Advantage over a tipi/lavvu shape is you get to use all the space right up to the edge, but that's about it. Personally I prefer the tipi shape for a tent but swmbo gets last call on this stuff. We'll be buying a 4m bell tent next year.
Oh yeh, and replace the guys with some bright yellow/orange climbers accessory chord or similar if you absolutely have to pitch anywhere near other tents. (hell is other people, as someone once said).
Best, Stu