Breach of Contract - Refusal to refund

I made a booking for Algeria campsite over Christmas. However, due to Covid we had to change our plans and cancel the booking - we did this more than 30 days in advance of our booking start date. According to their Terms and Conditions, we should be eligible for a 75% refund. However, after weeks of chasing, filling out forms, getting our band to stamp our account details etc - they are now refusing to refund us and say they will only offer credit against a future booking. This is pure breach of contract and we are looking at taking legal action to recover our funds.