[Neil Jones]

Do they tend to show the kids Christmas ones as a block of 5/6 episodes (think one series didn't have one) over the period.

Every series of the original show bar the first one had a Christmas special (they were the first of the respective series they were attached to, so they'd appear at Christmas time (or near enough) and then the next series would follow a few months later. They effectively became a "tease" to show what sort of games were coming up.)

But usually when repeated Challenge keep those separate from the rest of the run. On occasion they're been mixed in, but the trend is to separate them out.