Typically the British doner kebab meat will be made from a blend of sheep, beef, poultry meat plus beef fat, rusk, onion, salt, various spices, flavour enhancer E621 (msg) and emulsifiers E451(i) (Sodium tripolyphosphate - its a preservative) - Sample ingredients from one of a few manufacturers on the web.
You can also get things like frozen chicken meat on a doner 'pole' ready for cooking, made with various spices to alter the flavours, as well as variations to the spices used in making the doner.
The original doner,or gyros - there are loads of variations and types - is made up of marinated lamb meat with extra fat to baste it while it cooks over charcoals ' grills - served in a split warmed bread roll or pitta bread pocket with various sides like raw onions, chilli sauce, lettuce, tomatoes etc.....basicaly no squirrel, no cat, no rat - all tasty meats and spices....