For now, the problem has been solved! After posting this, I read through Tech1e's excellent post regarding the key signal being too low. (Link HERE -http://www.briskoda.net/forums/topic/281731-fabia-immobilizer-key-signal-too-low/) The post made an initial suggestion of - "If you are presented with a non start and an immobilizer light flashing (poss fault code of key signal to low) try first moving the steering column up and down and back and forwards, you would be surprised how many times this works, it's also a pretty good bet that there is a connection issue at this point."
This has solved the flashing immobiliser light issue. Now I'm aware there is a possible connection issue, I'll await my Haynes manual to arrive then crack on with having a look at it. Hope this helps. Thanks to Tech1e for his helpful post.