In answering Brian's question, if you look at this from a logical standpoint, at the end of the second round every member will have spoken once. If any party is going to get an opportunity to speak a second time, it makes sense that the party with the most members would lead that off.
Take yourself off the order for a second, the actual chronological order of who speaks. There are eleven members who are going to be asking questions; six are Conservative, five are opposition members. Everybody gets one shot. Regardless of what the order happened to be in the first and second round, in the next round, if there is time--and rarely is there a situation where there's time--it stands to reason that the party that would lead at that point is the party that has the most members on the committee.