The nurseries drive me balmy. Ours sells all that stuff that can't even stand a few degrees of frost. Someone has given me a Hibiscus, an orchid that actually says on it "no good for below 10 deg", and a tuberous begonia. I find it so annoying as many people must just do their dough. The hibiscus was from a landscape gardener, thanking me for lookiong after his horse!!!! I am not talking decidous hibiscus either!!
Jane, they used to have rosemary growing very successfully as a street shrub in Mansfield. We get lots of -7deg but they get quite a few. I would give it a go. You know you can easily grow rosemary from cuttings so you could take some and keep them. I have grown it in my garden. Good luck! Pam