I have also been ripped off by these con men cowboys. Do not even give them a chance to stay in business, Just tell everyone you know. My car had a "new" engine put in and they simply phoned me and said that unless I paid another £400 they could not install the engine. The guy on the phone sounded like he had just come out of jail.
Their gurantee is worthless as well.
DO NOT GO TO THE HEATHROW ENGINE CENTRE IN SOUTHALL - THEY ARE CROOKS AND SCUMBAGS