I got a standard 8x6 from
www.thegreenhousepeople.co.uk Based in Stoke on Trent, its got toughened glass. I know they do lean to's.
You can request a catalogue from them, but perhaps drop them a line and see if they can advise you of your specific needs.
The following are from adverts in the back of this months GYO mag.
www.greenhousebonanza.com www.greenhousesgalore.co.uk www.isgreenhouses.co.uk