Our restaurant booking was forced off the menu

We had to cancel a wedding meal due to the lockdown, but met a string of excuses

We made a restaurant reservation with Radici (part of D&D London) and paid a refundable £250 deposit for a family meal after our registry office wedding. When the pandemic set in we cancelled the meal which was booked for the beginning of June. We’ve now been chasing the refund for 11 weeks. We have had a string of excuses, promising the money is on its way, but have never received it. What can we do to get them to refund the money?

MW,London