After a bit of investigation, I've read an article which says they are both frost hardy mountaincrestgardens.com

Only reason to bring them inside is if they are being grown in a pot which is not frost proof. I have both of these on my rock garden and they have survived temps down to -18c.

You mentioned that your Container is a stone one,so they should be fine,preferably if it is raised off the ground ? I leave my Pottery ones outside these days,which aren't frost proof,but some are stood on pot feet,others on gravel.I guess it depends how harsh a winter we get this coming year.You could always cover them with garden Fleece ,or similar if you are in doubt,and remove it when the worst is over..

I have some sempervivums growing in a raised bed which I protect with a piece of rigid plastic shheting, supported by bricks. This is only to stop rain getting into them and freezing

Both grow fine in Flagstaff, Arizona, which is far colder than the UK. The only concern that I would have is drainage, since they hate saturated soil, or, as Owdboggy says, whether the pot is frost proof or not.

Thank you Camomile, Owdboggy, Bloomer, Andrew R and Tug for these replies, which are all so helpful. I can't move the container or lift and it isn't on a slope but I will add more grit and cover with rigid plastic during the worst weather and hope for the best.