As a young plant they do well to be protected (from the elements) as Andy has done, but as an established plant, say 2 years or more, they benefit from being exposed to normal growing conditions. By this I mean that what ever nature throws at them in the garden they will either crop heavy or lighter and there is very little you can do that will make a difference.
One example is Bramling Cross. They really thrive on cold winters. If you recall the winter of 2011/12 was a prolonged period of very cold weather. Come September 2012 I wasn't sure if I was in Sussex or the Amazon, the Bramling bines were so thick and heavily cropped with leaf and hops it took 2 days more than normal to pick that garden! This was also true of newer varieties such as Pilgrim and Admiral. 2013 was a walk in the park compared to the previous year.
There is no definitive guide to which varieties grow best in which conditions, it is only my opinion drawn from my own experience. Certain ones grow better in Kent and Sussex than in Worcester and vice versa. I must also stress that as we only do this as a hobby it is down to what varieties you would prefer to grow which may or may not be the best for your location. You may win or lose on the harvest size but I still say you win as you're growing hops!
