Good morning and thank you for you patience.
The issues of you spending time with/ speaking to you children and you supporting them financially are separate issues entirely.
You do have a legal obligation to provide maintenance for your children, and this is something you can't get out of even if you don't see them that often (or at all).
What you pay depends on what you earn, and you can use the calculation tool here to work out what it should be: https://www.gov.uk/calculate-child-maintenance
As I said though this is separate to the right your children have to have contact with you - they should be seeing you regardless of what you pay in maintenance.
You are going to have to try formal channels to reinstate contact I'm afraid.
Mediation has to be the first point of call as it is a legal requirement prior to issuing an application in the family court.
You start this process by attending family mediation - see here for a link to find your local mediator:
Assessments are usually around £30-£40, and the mediator will advise as to how many sessions might be required. Mediation is a collaborative approach and allows you to talk through issues and concerns in a safe and protective environment.
Following that, if the mediation does not succeed in a successful agreement, you can apply to the family court for a child arrangements order (see below description), setting out the living arrangements and contact arrangements that you would like to see.
You would apply on a c100 form, here:
You send 3 copies of this form to the local family court centre.
Alternatively, you can apply online:
There will be a court hearing after you apply and a family court adviser will be there in attendance too (from CAFCASS).
The application costs £215.00, and you can represent yourself so you don't need to engage a lawyer. You can also possibly get a fee exemption if you are on low income/have low savings.
For this you would need to fill out a fee exemption form: http://www.gov.uk/get-help-with-court-fees
I hope that this answers your question?
Thank you for your enquiry today. I am happy to answer follow-up questions - please do get in touch with requests for extra information or further queries and I will do my best to help you.