I used a centre punch on the two security bolts and they popped out quite easily! I was bloody happy with that, I thought that would be the hardest.
Put the new one in and bolted everything up, fortunately DID NOT snap tighten the new security bolts as when I bolted everything up, as the barrel was hard up against the dash. The mounting bracket is slightly different than the old one.
I ended up putting two washers in the steering column bracket to drop the righthand side down and it now works fine.
I drilled out the pin in the old one as I was going to swap the barrels, but then tried the washer idea and it worked fine. Now I have a key that doesn't fall out of the ignition and two doors that unlock with the same key!!!
