You have to understand elhuerto, that not all of us old duckers are terribly mectric wise. From my calculations the greenhouse you are thinking of buying is 8'x6'.
We have one, of that size, which would be £50, collected. It is glazed, glass included.
I would avoid polycarbonate like the plague. It is too flexible, and on a windy day the panes of your greenhouse could be miles away.
valmarg