We ordered a tumble dryer online and the company failed to deliver within 6 weeks. The company then said they would upgrade from a 6kg model to an 8kg model as a gesture of goodwill. The difference in price is around £300. On arranging delivery the company have now said that they cannot send an 8kg model as a replacement but will send the 6kg model with £50 of store vouchers as compensation. Can they do this?