Yea silly me what sort of Alarm system could be disabled in this way!!!
I will investigate the lock when I get chance, already removed the fuse and this has stopped the problem, now the keys work only, bit of an incovenience but I had wondered how this effects the immobiliser? How is it set etc.
Having only had previous experience of Mini's, MGs and other easy to understand cars I am finding the modern electrics a bit daunting, coded keys, computers etc. I have sent off for the Paul Hardiman MX5 Renovation Manual, hope this will include some guidance on electrics