Hi Dave
As others have said, I much prefer to use decent hole cutters ( As per Spuds link )
On soft stuff like GRP I normally use my cordless drill .... I tend to go a bit mental with the electric drill
If I am worried about cocking things up, i'll measure a gazillion times, mask the area off, drill the hole 1 size smaller than needed & fettle to size with my die grinder or round/half round coarse file .... Well, you lot know me, like to do it the hard way if at all possible
