Hi Alasdair,
Great scope you have there.
I agree with Astropic as first place to check might be the rubber o ring
There are no tips or tricks because there is not supposed to be a wobble.
For the OTA connection wobble, first thought is have you tightened the two nuts and bolts securing the mount base to the OTA?
As to the finder scope itself wobble, the two adjusting thumbscrews ans the third non adjustable spring loaded pin are designed to hold it firm.
Check to ensure it is assembled correctly per the manual.
Good luck with it.