Thankyou for your lovely supportive replies.
To answer your questions. I have always suppported the children to have contact or not to have contact with their dad as I believe it is their best interests to be free to make that choice. In terms of the emotional impact on the kids, at the end of the day he is their dad and there is worse in this world, he doesn't drink, take drugs, hit etc, just totally controlling and manipulative so that you always find you don't have the space to be you. My daughter rightly so at 16 has decided she can't stand being with him anymore. As you can imagine a 14 year old boy desperately needs/wants a dad in his life.
The issue with the move is not about removing them from dad. I support contact and have always done what I feel is best for the kids. The dad can easily relocate for a couple of years, he works at sea more than 50% of the year, doesn't want to be living in Cornwall, blames me for that, and last summer was looking to buy a flat in Sydney. I will continue to support contact.
I have just finished 4 years retraining so that I can be economically self sufficient. For those of you that know Cornwall you'll know that jobs are difficult to come by. The combination of well paid jobs, extensive family, and simply we all want to live in OZ is the reason for the move, all equally important. Trouble is once a court order exists for contact I have to provide an air tight case for going and Ex-husband is fighting it. He is manipulative enough to half aggree, ie in 2 years from now, to look good for others and the court, but I have 20 years of experience of his behaviour and he has already suggested that at that time ( after 2 yrs) he will offer my son to stay in UK and finish A levels here. The point being none of it is about my son's best interests. It is and has always been simply about him getting the uppper hand. I could go on about all the things he has done/said to support what I'm saying but I'd be here forever. My own mother even finds it hard to see his behaviour or to understand it as my ex is such a smooth operator you need to be on the recieving end of it usually to see/ experience what he does.
So basically I need solid tangible reasons to present to court on why educationally it is better for the kids to get there by the end of this year ready to start school.