I suggest you contact a solicitor who specialises in family law for advice,
I don't know the details of the break up but I wonder if Is it in your sons best interest to be so far from his dad, could your partner not relocate so you can stay closer to your ex or wait a few years until your son is old enough to travel to see his dad on his own. If your ex has to do a 120 mile trip to see his son he may find it difficult to maintain frequent contact or is that you or your new partners hope.
its the north east and im the north west of england. access agreement is every two weeks friday 7pm - sunday 7pm....doesnt see them at all during the week but watches football on the sunday in between. he texts sometimes but not always!
up until 4 years ago he was a great dad but things change and definilely have done in his case.
Personally, if he was seeing my child in the week as well as every weekend then I would choose not to move
However, as he only sees him every other w/end I would have no hesitation in moving.
He has no grounds to stop you anyway unless you wanted to move out of the UK, which you don't so I wish you a happy moving day!