Supplier not delivering goods as agreedi

I placed an order with another small business for some hair products a few months ago, with the agreed delivery date to be beginning of December. I paid a deposit and then they confirmed that they would be despatching the products earlier in mid November so I paid the balance in full, as it was agreed to pay before goods are despatched. I kept then being told they waiting for this and that which has caused a delay in production, which meant I have been constantly chasing to find out when I will be getting my goods.

Today I received two thirds of the order, and still no definite date when I will receive the rest. These are gift boxes which I need to send out by next Friday, as I advertised they would be despatched to arrive before Christmas. The supplier has been made aware of my deadline, as I need to pack the boxes which takes an age as its over 300 boxes. The supplier just keeps fobbing me off and I need to make sure I get these products or I will potentially have to refund alot of people and have my business reputation in tatters.

Is there any recourse or legal action I can threaten them with? Really desperate to get this sorted but dont know how else to get through to the supplier who seems not to be bothered.