You *are* talking about England -- the home of belts-and-braces people. That is, take everything just in case. It's likely that they had few extra tops ranging from fresh jerseys to windvests to showerproof to heavy-duty storm. Possibly a thermos flask, plenty to eat, and a few other items of clothing to suit each change of 5 deg C in the weather; things such as booties, leg warmers and tights, long-fingered and heavy-duty gloves. Plus probably three or four tubes and a toolkit so they could rebuild the bike on the side of the road if need be.
I did a century on Sunday, too, but didn't take anywhere near that stuff. It all fitted in my Topeak rack bag, and for the first time in a long while, I left the handlebar bag behind.
But... you were on a road century... couldn't you ask someone?
