According to JTIS, you do the following,

1. Turn ignition key to position one.
2. Release the retaining tang.
3. Remove the ignition switch lock cylinder.

The 'tang' that they refer to is likely to be a locking pin or something similar.

 

Thanks for the info but unfortunately I cannot get the key in far enough to be able to turn it due to the small piece of plastic, I need to know how I can remove the complete barrel assembly. I've managed to unplug the electrics to it but cannot see how it is removed

 

Was afraid of that, but thought that you might be able to get the key turned to position 1.

As Tricky says, look for the heads of the shear bolts, they will look like rivet heads.

 

The steering lock assembly will have been fitted using shear bolts for security. You are looking at either hammer and chisel or electric drill to remove them, I would try holding the key flap open and see if you can get a small knitting needle down the barrel and hopefully get the offending bit of plastic tube to slide over the end of the needle and then you may be able to withdraw it. The tumblers in the barrel may be a problem in doing this as they will try and drag the plastic off the end of the needle but it's worth a try.

 

Try a piece of wire thin enough to go down the barrel and bend the end over to make a hook, then pass it past the piece of plastic and try and hook it out?

 

Don't put anything with a hook down the barrel or you will get that trapped in the tumblers. You could just bite the bullet and ring an auto locksmith, less chance of doing more damage plus I am sure they would have come across the problem before.

 

Thanks guys for the suggestions, I've already tried a straightened out paper clip with the end bent into a small hook but I can't even see the bit of plastic if I push open the spring gate and shine a light in, I'm now thinking it is behind the gate. I can only get the key in about half way.

 

It can't be behind the flap if the key only goes half way in it has to be half way down the barrel. Any idea how long the plastic bit is ? You will not see it with the flap open because the tumblers will be down, do a google for tibbe locks that will give you and idea of what your up against.

 

Quick update before I dash of to my parent's for Sunday dinner (Wife & Daughter away for the weekend)
I took trickythejagman's advice and called an Auto Locksmith (not expecting much joy on a bank holiday Sunday) he was round within the hour and informed me that this is quite a common occurance (So I'm not the only idiot in Teesside!!).
It turns out that I had managed to flick the offending piece of plastic out but hadn't noticed (found it on the car later) but the tumblers where out of alignment stopping me getting the key fully inserted. The locksmith reset the tumblers which then allowed the key to be fully inserted.
I've made a start refitting everything I had removed so hopefully about an hours more re-assembly and car will be back to normal
Thanks again for all the advice guys