Bought myself a mini greenhouse from Wilko at the weekend
http://www.wilkinsonplus.com/invt/0273090Looked quite sturdy and the plastic better quality than some I've seen, but the instructions are cr@p and I've managed to crack several of the fittings that the poles plug into, as I did it in the wrong order (ie tried to build it from bottom up, rather than front + back separately then join it together with the side bits last). Might also have helped if I'd read the instructions rather than just looking at the picture..
Havent got time to take it back this weekend so have gaffered up the fittings and hopefully that should keep it in place til the end of the season.. when I shall take it back and get a replacement for next year!