When I'm sparring (tkd) I'm always against someone smaller than me so It's always realy hard to get some real practise in because they'r always beating away at my ankles and i's no challange. Any ideas on how I can imrove my sparring without actually sparring?
Can you be a little more specific? How old are you, how old are the people you are sparring, how tall are you, how tall are the people you are sparring, how hard are you allowed to hit?
Personally, unless sparring someone vastly under you skill level (like sparring a 8-year old yellow belt), you can improve on something. You just need to look at how you go about your sparring.
Sparring someone smaller than you who keeps "chopping your ankles"? Work on your movement. This is the time to learn how to use your angles. Working on moving quickly, time your movements, and learn how to more effectivly counter so you can put them into inferior positioning. When I spar children I work on my foot work and not worry about striking. Kids are relentless and since you can not really hurt them or hit them hard you had better have excellent foot work to keep them from chopping up your legs.
Sparring someone with much lower expereince than you? Find out something they need to work on in sparring. Maybe they need to learn how to follow up with combinations. Maybe they need to work on blocking. What ever. Spar one-dimensional for the most part so they can focus on that aspect of sparring while you focus on improving what ever you are using to help that sutdent improve. They have a pretty good idea of what is coming, so you need to work double time on being deceptive, tricky, fast, etc. to make what ever you are doing work.
I could go on and on, and no body wants that

, but try to at how you can improve with the people you are sparring.