Went shopping in my Morrisons this week & found they're selling quite large greenhouses!!!!!! It's got a plastic frame with clear plastic cover which ties to the frame. Has a zip up door & an air vent.
Not entirely sure how big it is as the measurements were in those damned confusing millipede thingys. I'll have a better idea of size when I get it erected in my back yard.
Only cost £20 ( rest of my shopping only came to £7)
CC