No, they're perfectly hardy, shouldn't be any problem at all - just don't put them somewhere really, really windy.

Thanks Bamboo,

I suppose it must depend on your latitude and whether they are exposed to early morning sun. I have 2 Bay Trees that I've had for several years now and which I reckon are pretty good specimens, but I make sure that they remain frost-free. Past experience shows that only one careless moment with frost overnight then early morning sun will brown the leaves with catastrophic leaf drop, and a year disappears at a stroke. I write from Edinburgh, not quite the North Pole, but I daresay even Herts gets the occasional frost followed immediately by sunshine? If you look at my plants on this site, you will see what I do. If I lived in Herts I would at a minimum cover them with fleece from now until April - but bow to local knowledge provided by Bamboo in your nearish neighbour of London. It's the sun on the frost, not just the frost, that's the danger. All the best.

I put one in around 4 years ago it was 4 feet high and dieing, planted it at the side of my house, which never gets any sun now its about 12 ft high.

Good point, Scunnered - but the only problem I've found here on the outskirts of London really has been wind damage with these. We do get frost, but generally our temperatures here are probably higher than yours, even when its frosty, you being up there in the chilly zone! On the other hand, many plants, even here, do get damage when early morning sun hits frozen buds or leaves - but usually, it'll just be a light frost, not actually frozen.