While ever there are no orders in place, both you and the father can do as you please, so it is important that you begin the process to get orders in place.
First, I would speak to Legal Aid and seek advice. They can offer it free with an appointment. You may also be entitled to funding for a Legal Aid solicitor, but hopefully it doesn't get to that.
Second, organise a Family Dispute Resolution conference with the outlook of putting a parenting plan in place that stipulates neither parent can relocate with the child if such a relocation significantly impedes on the child's rights to have a meaningful relationship with the parents. If the father agrees, you can have a parenting plan made into consent orders, which gives the court power to administer penalties of either parent contravenes the orders.
Third, if the father moves before any of this can occur, you can file an urgent recovery order. At seven months of age, I assume the child is still breastfeeding, so hopefully it would be acted upon swiftly.
After that is very much circumstance-dependent. I hope this helps.