We've just had a slate floor put down in a small cloakroom and the
plumber is back to refit the toilet in a different position tomorrow.

I've tried it in the proposed position but notice the pan is likely to
end up with a very slight wobble if nothing else is used other than
the original screws when it's fixed to the floor. What solution should
I be checking for to make sure it's a good fix with no gap / rattling
etc?