Posted: 05/11/2013 at 21:34
have a look at this.
The RHS system is better for this country. American zones are somewhat different because of areas that can be very dry and cold, whereas in Britain in winter we are usually wet and cold.
Also you have to remember that even in one garden there will be microclimates, frost pockets at the bottom of slopes, warmer bits against a south facing wall, etc.
In Doncaster, Plants will need to be fully hardy to at least - 10 C to survive the winter outside.