I made a little progress with the dash as well.
The old dash template was fixed back on and the steering column fixed in its optimum position.
I then set about taping card around the hole until the card was just touching the steering column.
Steering column removed, the new dash was fitted over the new one and the card circle used to mark up the new dash.
A few double checking measurements later (fingers crossed) and the hole was cut with the trusty dremel. Still needs a little tidy up but it's in the right place!
Apologies for the state of the footwell which seems to be a detritus collection device at the moment.