Yeah syd, they say when a cat wags it's tail, that's it angry, and when it purrs, it's happy, but it can mean the opposite, my cat Pebbles is ALWAYS wiggling her 2 inch long tail, because she knows I like it.. and she's always happy when she does it, kinda like a puppy.
It's so cute, because I say to her 'Where's your Fluffy Twirly?' and she looks back at her little stump of a tail, and wiggles it in response hehe
They reckon cats HATE their tails touched, all 5 of mine LOVE it! especially Tails, he stiffens his tail so I can stroke it [that didn't sound right, but no other way to put it ]