i got a gardman greenhouse last october in there sale 8 x 6 made of 4mm polycarbonate,it cost about £300 with base,staging etc i put it up in February this year,it is the best greenhouse Ive ever had,my plants this year are the best ever,so easy to erect and very solid,the polycarbonate is supposedly 20 times tougher than glass,and with my grand kids visiting quite often i thought it would be safer than glass,the only thing extra i bought were glazing clips from wilkos (they are the cheapest) £1.69 for 25 clips just to be extra sure just in case we got strong winds,i hope this helps