That's ridiculous, and worse they should know it because their own hutch buying guide has the RWA etc. guidelines. I've emailed them.
Find me some more I'm on a roll
A few more!
http://www.amazon.co.uk/Business-Single-Rabbit-Guinea-Shelter/dp/B00CQ7H7MO and http://www.amazon.co.uk/Oypla-Single-Rabbit-Hutch-820x390x700mm/dp/B00HU8SXPE
http://ukpetsonline.com/SearchResult.aspx?CategoryID=131
http://www.rabbithutchwarehouse.co.uk/hutches.php (some bigger hutches but also some very small ones)