It's no good waiting for Santa mate - you have to get out there and make one. Greenhouses don't just materialise out of thin air lots of different kinds of artists have greenhouses!!
Don't worry Eileen, it's safe, it stays indoors with the others, I don't really want it mixing with all those awful prickly things.
All of my greenhouses over the past 30 odd years have been on a similar design as Ziggy's cactus house. I have found that timber and tunnel polythene is very practical. Even if the polythene splits, it is easy to repair with tape as long as it's on a timber frame. The timber is also practical as you can fix into it far easier than metal. Making staging and shelf space is a doddle, and a second internal skin of bubble wrap (large bubble) makes a good two degrees difference in the winter.
Zigs, that is SO sweet! I used to dream of a Greenhouse where I could grow herbs and supply restaurants, thereby making a fortune! (Dreamer!) Now I am satisfied with gardening to feed the two of us and giving the surplus to our neighborhood.
I think I will use a translucent white. I know the catholics will be sad, but I do not mind being blinded by the white light. As long as it is not directed at me that is?