Is this a Sempervivum?

Yes. or commonly Houseleek.

Ta. very much. I wasn't sure.

It is probably a Sempervivum tectorum variety. There are now several hundred different named Semps. many of them hard to tell apart. especially as they tend to vary greatly in appearance through the year and whether in sun or shade. Best results are from growing in full sun and not overfeeding. They are a very addictive plant to collect.

Definately a Sempervivum but to me a lot of them look the same, so can't help with which one, would need a Sempervivum enthusiast/expert i think :)