So prior to two years ago you were living with your ex, drinking heavily, checked out of your marriage, leaving her with the kids when you went down the pub.
You split and you started working away. You say that during that time you stopped drinking heavily, although you still drunk on social occasions
You got frustrated that she kept talking about your drinking, and couldn't see you werent drinking as much, but you weren't actually in the country at the time
You decide to drop everything and come back and seem frustrated that your ex didn't immediately drop her entire life she's built up whilst you were away leaving her to parent your children by herself.
You gave her a whole 7 weeks to operate to your timeline and then initiated a divorce, which is absolutely your right to do so.
Your ex understandably may have reservations around contact with the children due to your previous alcohol habits which she has not been able to witness you changing because you were not in the country. You have potentially had no regular weekly pattern of contact with the children because you were working away.
And it's pretty unclear whether you are actually paying any maintenence.
You seem to think the fact that you were paying £1000 a month makes you a good dad. And absolutely that's way better than some of the deadbeat we hear about. But the fact that this woman is willing to forego the £1000 a month, a not insignificant sum, in an effort to keep the children from seeing you tells me there is a lot more to this story.