Cousins Estate Agents in London

Please do not use the Cousins estate agents in Tottenham N15, they are very dodgy and very unprofessional. We were buying a property via different estate agent, (we had been registered as buyers at Cousins too), Cousins had been advertising the same property for sale previously. On the date of exchange of the contracts we were told that Cousins had sold it to someone else. The vendor had been selling the property for 2 different people at the same time, we and our estate agent did not know about this, Cousins did. When we called to them to complain, the woman on the phone laughed at us! We had just lost our new home, £3000 in fees and our buyers. Just disgusting behaviour and I would never use them for anything, they are lacking of any morals and caused my family massive grief, a week before Christmas.