habitation and gas checks

I bought my motorhome from a dealer.the dealer employed a fitter who works under the flag of the Approved Workshop Scheme to carry out a habitation and gas check, . this fitter signed that everything was OK but left most of the faults to be rectified by the dealer,unfortunately the work was not carried out and we had a fire in the grill of our cooker caused by a badly repaired gas pipe and the spark igniter was completely missing, The Approved Workshop Scheme stated that the fitter was not at fault and I should take the matter up with the dealer ,and the signed certificates were only valid on the day they were signed.The AWS also stated that it was OK to repair a gas pipe but the person using the appliance should be warned it could be dangerous there must be hundreds of motorhomers out there with useless pieces of paper