Maybe I'm Wrong but...
I think you have your echeveria and your sempervivum mixed up.
I bought a plant that looks exactly like the sempervivum images on your site but it is labelled an echeveria and google seems to corroborate that my plant is in fact an echeveria.
Hi Sam, these two plants do look a LOT alike, in fact, several of them are pretty hard to tell apart even to an experienced grower; the biggest differences between them are that Echeveria are not frost hardy (in most cases), they also are perennial, and produce their flowers on a stalk that emerges from between the leaves, and after they flower, they continue to live and can flower multiple times during their life span.
Sempervivum, although related to Echeveria, are extremely frost hardy, and originate in high mountains, where they can actually continue to grow even under the snow; they also bloom, but in their case, the rosette elongates into a flower stalk, and after blooming the rosette dies.
In some cases, the only way to tell them apart is that the flowers are produced so differently, and also, Echeveria left outdoors during the winter generally won't survive.
So, if you are sure that what you have is an Echeveria, treat it like an indoor plant for the winter, and give it a summer outdoors for the best vigor.
Hope that helps,