Thanks for that.

So the way I have been doing it is probably the best, I use a drill press vice ensuring that the drill bit (same size as the original hole) is free to move through the hole, I then tighten it down just sufficiently tight to ensure that it does not move. Then using icremental drill bits, in this case 10.5mm through to 12mm in .5 mm increments I allow the drill bit to find it's centre and slowly drill each succesive size bit until I achieve the desired size.

Good to see that I was on the right track then!

Thanks again,

Peter