Key fob and steering column receiver fault

I have a 2002 1.8 Zafira auto. Every time I try the key in the ignition the engine fails to start. It has spent most of the last 3 months in the Vauxhall Dealers who can't find any fault with it and suggested I stop using my mobile phone whilst the key is in my pocket! I picked it up today, went home then went to go back out again and it wouldn't start. I called the AA and a very nice older guy rolled up, took the key, banged it on the underside of the steering column and hey presto! The car started first go. He said it was probably a fault either in the key or the receiving ring. Firstly, I have paid Vauxhall over £200 and they failed to find a fault, secondly, do I need to replace the ignition lock or key? I was that stunned when the AA man fixed it so quickly I forgot what he said. He did say older keys can be affected by static but not this one. What do I do now?