Posted: 11/05/2012 at 20:38
Hello and welcome.
Best advice that I can offer is to get the largest greenhouse you can afford and have in your garden. Over a short time you will fill it up, esp over winter.
I would say that a wooden greenhouse with glass is best option. Metal frame with glass or plastic comes second. Those lightweight plastic bag growframes that you see are not really worth it.
Getting electricty and water in the greenhouse is also something you should plan for.
Location - west facing if possible, also sheltered is good as you do not want it to smash in strong winds.