Vauxhall Corsa engine

My corsa has been in the garage for 9 weeks now due to various problems but recently they have found a fault with the piston and have informed me I need a new engine which is covered under the warranty. They fitted a new gearbox recently and they had to check the ecu to make sure is was still standard and had not been modified, all checks come back clear. Now the engine needs replacing they had to send the ecu to Vauxhall in Luton who then passed it on to a company in Germany who have come back and said the ecu has been remapped. This company will not provide any proof that this is true. Has anyone else suffered any similar problems ?