Lat year, I put mine up in a sheltered corner of my back garden, but later in the year. I think they are suitable for bringing on seedlings when the weather gets warmer, and hopefully, less windy.
I bought a large plastic greenhouse off ebay last year (before I got my real one) I only had it up a few days - a few gusts of wind and it was, to put it politely, no good! The wind had even ripped the anchoring holes from the pegs which were supposed to keep it in place!
I havent had any problems with the small ones, but they were put outside later in the year. They aren't intended for allotments methinks. I guess you "pays your money and takes your choice" unfortunately, some of us don't have lots of £ to spend.
I'm actually using a couple inside my greenhouse, as a "mini greenhouse" this year and am having good results so far.
Bernie aka Dexterdog
PS Andrew - I spent my uni days in Cardiff (Llandaff) (way back in the 1980s) whereabouts are you? I know there has been a lot of investment in Cardiff and if I came back I probably wouldnt recognise anywhere! Happy days and happy memories!