Hi Anaana and welcome to GoY most of us wouldn't have a clue as to hardiness zones the majority of the UK is 8a or 8b with a very small amount being 9a. Copy and paste the url below into your web browser for more information (not Google!)

http://www.trebrown.com/hrdzone.html

What do you mean? There is more to hardiness than minimum temperature. Plants that grow well in say California should grow in parts of the UK looking at hardiness maps but they do not - as we do not get the high temperatures in the summer and the light intensity in the winter and summer (where I live in east central Scotland it can be light only between 9am and 3.30pm in winter). In Johannesburg, ZA, it can get to minus 3 at night and 30 in the day, so plants can survive having 12 hours of sunshine and low temps for a 12 hours at night. So light and duration of that light is as important as temperature.

The American hardiness zone system is largely irrelevant in the UK as it is designed for a continental climate which is much drier than our maritime climate.
The most commonly used UK zone system is the one used by the RHS which is simply divided into zones 1 to 4 and totaly useless to you in Canada.

I have a book which shows zonal systems for UK and most of Europe, and its the same scaling as the American zonal system. But you'd need to ask about specific plants - the RHS 1-4 rating is used to denote hardiness rather than zonal ratings.

Bulba's comment hits the nail on the head. Take spring flowering Pleione as an example - USDA 9 to 10, but read up on them more and this is under the proviso that they are dry when cold.

If you look at a N.American hardiness map (http://www.completebamboo.com/Pic%20Assets/Other/2006_Hardiness_Zones.jpg) then most of the UK has the same hardiness as Texas, Louisiana, California and Georgia etc. Hardiness is not the same as climate to be fair.

Our Royal Horticultural Society has a wonderful A-Z of garden plants which gives the minimum temperature they will survive and lots of other tips for each plant listed. It includes plants from all around the world so you might find a copy on your shelf will answer your questions. (Though the postage to Canada would be a bit pricey)
You may find there is a similar publication for your country.