How long would it take to lose about half a stone doing pilates and how many times a week should i do it?

im not fat, im actually just under 8 stone and im 5ft 4 so i dont tink i need to lose weight however i really need to tone up and ill admit it im quite lazy so when i did used to do a workout dvd at home i used to dread it and started makin excuses for myself. i enjoy pilates though, its relaxing compared to jumpin around and stuff, iv never done any cles i dont have time and cant afford it, just following a dvd of it haven't done it in about a month. anyway, on xmas hols from college soon and id like to tone up while i have the time off, how long should it take to start to see changes in thighs and bum and how often should i do a pilates workout? i really wanna do this cos iv been tellin myself for 2 years now to get into tiptop shape but i always end up givin up!