>  I have set the framerate down to 20 and it makes a difference (comes 
>  down to 45-60 CPU use), but it is also slower of course.
>  Is there any tutorial where I could check optimising tricks or 
>  techniques?

You might also look at how you're polling events and see if you can 
choose a method that is less intense. No need to keep looping if you can 
just stop and wait for the next event. You might try to cut back on how 
much you're drawing to screen each frame. See if you can update only 
part of the screen each pass and possibly only update changes every 
couple passes.