Hi,
I use 'Ben's 100 Safari Strength Insect Repellent', bought from a chemist (if you decide to look for this one it's in a bright orange bottle). I've never had any bites when using this!
However, any insect repellent with a high content of N,N-Diethyl-m-toluamide (DEET) (the above one is 95% DEET) is effective.
Hope this helps!
Dan