Thank you for that additional information, that will be helpfull in allowing me to advise you today.
You need to call and speak with your partner calmly or email / text so you have written evidence of doing so.
Advice her that you want and need to see the children and despite what ever has happened between the tow of you you still need to be the father.
If she ignores this, then I would advice instructing a local family law firm. It may be possible to obtain legal aid that would need to be discussed with them.
The following link will allow you to look for a legal aid law firm.
Enter a local post code, select the area of law, ie family, crime etc and a list of local firms will be displayed, then all you do is simply call one.
They can write to your partner and advise her of your legal right to at least see your child.If she still ignores or refuses, then they can offer mediation that you both attend then as a last result, they can commence legal proceedings at court for you to seek a formal child arrangements order for the court.That would set out who has custody, you , her or shared, how often and when and where the children can be seen etc.