Cabbage & Broccoli

A week or two ago my Sister-in-Law, Sonia, gave me some plants that she had left over after planting out her own.
I've hung onto them until it looked like we were unlikely to be getting any frost. Planted them out a couple of days ago and been watering them to get them established.
Now, on the weather forecast, they say we might get a frost tomorrow morning! They should be ok though, brassica's are pretty tough plants.