Help - car has died.... ECU ??

apperently they checked all the drainage holes which were fine and the only conclusion we came to was that when we had the recent snow I didn't drive the car for a few days and that cos I didn't clear the snow off the windscreen it would have melted down through and got to the ecu... Basically the case of the ecu is nowhere near watertight - it has a screw in each corner holding the two half's together. I wouldn't advise anyone to pressure wash their s8 engine thats for sure. ! On later ecu's there is a gasket around the lip of each half to help protect it.
The ecu itself had blown about a dozen components and all the contacts down one side of a chip burnt so I didn't really fancy a try at repairing that......
Just for info the garage I used was Kartechnik in Poole and I was really impressed with their knowledge, not cheap but really know their high end motors......
With the radio, I know man who knows a man who knows a man who knows an audi master tech who can apparently sort the code out for free, says its a 1 minute job. Unfortunitely its taking ages to hear back from him.......
So whats the deal with the warranty then?? - does it cover the gearbox as that is my main concern, and how much '£' would we be talking......