Hello, my name is ***** ***** I am a qualified lawyer happy to help you today.
You can apply for a child arrangements order if your ex does not let you see your child. You will need to contact a local family mediator first before applying and you can do that here: http://www.familymediationcouncil.org.uk
The mediator will do an assessment which is usually around £30 and then recommend a few follow up sessions. They should be able to tell you if you qualify for legal aid.
Once you have done that, you need to fill out form C100 (a copy of which is attached) and send 3 copies to the local family court centre. There will be a hearing after you send that form in and a family court adviser will be there in attendance too (from CAFCASS).
The application costs £215 payable to HMCTS (by cheque or over the phone if you ring your local family court centre). You can get a fee exemption if you are on low income/have low savings. You would need to fill out a fee exemption form (http://www.gov.uk/get-help-with-court-fees)
The court will likely grant a child arrangements order if it would be in the child’s best interests. The courts encourage both parties to be involved in their child’s upbringing. Reasons why a court may refuse would be if there is a history of domestic violence or alcohol/substance abuse, or another reason why it would not be in the child’s best interests if a contact order were to be made.
I hope this helps - if you can please accept the answer and give me a 5 star rating (there should be a button on your screen to do this), I can answer follow up Q&A's at no extra charge and Just Answer will credit me for helping you today.