I would write back and say that the order is clear - on or before 9th March their client had to clear the mortgage and pay you a specified lump sum. That lump sum is £640 short and their client has frustrated the implementation of the order. You can apply to the court to implement the order and seek your costs of that (which will be the court fee) and the payment of £640.
With any luck the solicitor will advise their client to pay up as it will cost more to argue the point.
Thank you Charles,
I don't have to pay costs as I'm on Income Support due to having a disabled daughter, I'm not sure if he would have to bring his solicitor or barrister
to a court hearing but either way it will cost him & hopefully he will pay up before it gets to court:)