Dear Lee, zones do not work! Even the American Horticultural Association admits that! For according to the zones the Shetland Island which are off the top of Scotland are zone 8.
That is rubbish, as no trees can grow there due to wind off the north Atlantic and the next stop from the Shetlands is the north Pole! It is completely frozen in the winter and you may get a decent day in the summer. Yet is is in the same zone as a lot of major US cities as they do not take into account all weather conditions!
You cannot tell me that a barren place like the Shetlands is anything like what you have and you are zone 7.
Members of the jury I reat my case!
Neil.