B@W,
Here's another link at a more realistic price! UK as well and you can order online.
Assuming you're drilling holes for fasteners etc, this
Step Drill will be perfect.
Also, cover area to be drilled with masking tape and drill from the gel coat side. Take it nice and easy at SLOW speed. Once you have the size of hole you require, use the next shoulder on the bit to put a chamfer on the edge of the hole. Helps to stop the gel coat cracking through use.
Cheers,
Neil