So I have new Acrylic bath, new mixer tape for it with what I'm sure
is 3/4BSP threaded tails. (To be connected to 22mm pipe)

And I need to drill holes in the bath to make it fit.

What size drill do I need? Or do I use a hole saw sort of thing? The
chuck on my Bosch is only 13mm too...

All advice appreciated!

Gordon