If you tortoise is an adult one and it usually lives outside in your garden it simply will not survive the UK's autumn and winter temperatures as they become comatose when the temperature drops too low for them. The only way to keep them awake would be to bring them indoors and allow them free space in which to roam as if they were outdoors, which usually just isn't practical. If you have a grown up tortoise it should be in hibernation in a box of dry leaves or shredded newspaper by now in a dry, frost free garage or shed; otherwise it will not survive the winter.