Got it under control!
Changed guide exposures to 2 sec, might try 3, and the calibration steps to 20 and all is very good apart from an unusual problem.
I have the filter wheel pointing up and the OAG and Lodestar pointing down. After one or two exposures, MaxIm locks up and I have to do a full reboot, re-centre etc...
If I then take the Lodestar out and stick it back in the guide scope, it goes all night. I am not willing to rotate the OAG up as I am working on a project and and don't want to have to take all my flat frames again. When my project is finished, I will set it up the other way and see what happpens although I am very happy to basically have it working.