Immobiliser kicked in??

[lagunawoody]

I have a 1991 Turbo II Convertible which I bought about 6 months ago and it has been running like a dream ever since.  Started on the first turn every time.
 
When I bought the car I was told that the alarm had been disconnected and I have had no issues starting until last week.  I was under the bonnet sorting out an un-related issue and I noticed that one of the fuses, mounted in a small fuse rail on the RH (looking in) inner wing, had blown.  I replaced the fuse and as soon as I connected it the alarm, which I was told had been disconnected, went off.  I disconnected the fuse and after a short delay the alarm stopped.
 
The car now shows all idiot lights when I turn the key and the starter motor turns over strongly, however it will not fire.  My guess is that the immobiliser has been triggered but I cannot find any information what so ever.
 
I understand the security issues regardin information on alarms etc, but I need help.  Does anyony have any info or know someone in the Milton Keynes area that can sort this out for me.  I have contacted several auto electricians and no one wants to know.