I only have the Terry knickers, not the Bella knickers, but I always liked the Terry knickers quite a lot. I love the Dryline fabric, which is comfortable, wicking, and supportive enough. However, last winter I got a pair of Shebeest Pedal Pushers, and their fabric seems to be every so slightly nicer than Terry's and the chamois feels a bit more comfortable.

Having said that, I have another suggestion. You could just get some unpadded tights or knickers and wear them over your favorite shorts. I live in Florida and this is how I ride through what passes for winter here. Or you could just get some knee warmers--I think TE has some on sale now. This way you have a layer to peel off if you warm up.

Have fun on your century rides!