My glide approaches weren't the greatest when I did my skills test. However, try not to get too hung up on it. If like me you'll do the nav section first and will have been concentrating that much doing nav etc that the circuits at the end are the easy bit.
Besides, if the glide approach is the only bit making you nervous then remember they do have partial-passes. It's not the end of the world if you cock that bit up, all you'd have to do is re-do the circuits section in a week or so- not the whole thing.