3 years old and coil pack and spark plugs erroded?

Hi I'm just after some advice really I purchased a car in Feb 2012 a new vauxhall corsa, now I have started to have problems with it Took my vauxhall corsa to an independent garage who could not diagnose the fault because of a fault code for this problem was unavailable and could on be detected by equipment held by vauxhall garages. After contacting vauxhall and waiting a week to get an appointment, vauxhall discovered that it was the coil pack and the spark plugs in my car that had corroded. Can this surely happen after 3 years, (when I nearly collapsed) after vauxhall had quoted me £350 approx to fix this problem I asked how this is caused, the answer I received was general wear and tear, your advice would be helpful as I'm thinking of taking this matter further as after some research this seems to be a long standing issue and frequent problem with vauxhall corsa's.
Thanks in advance.