Ok, inside an Aerodrome Traffic Zone (ATZ), you can't fly a kite more than 30m above ground level. An ATZ is 2 nautical miles or 2.5 nautical miles in radius, depending on runway geography (length of longest runway being main consideration). As the Isle of Man airport is pretty small, the ATZ is only 2 nm in radius. However, as you can see, if you are flying your kite below 30m above ground level (I use 25m lines to comply with this), then you aren't breaking that (kite specific) part of the law.
Outside of an ATZ, you can't fly a kite above 60m above ground level. Both that and the 30m above ground level inside an ATZ can be gotten around with written permission from the CAA.
Does that cover everything? Any questions and I will be glad to try and answer them