Just thought I'd tell you that I got in touch with a man on opuntiauk.com. He sells cactus pads for tortoises at a reasonable price! You can email him or he has some for sale on eBay at the moment- hardy outdoor yorkshire opuntia humifusa prickly pear cactus. If you miss it his seller name is - epalgilly. He says he grows opuntia in his unheated greenhouse and has them outside! 
