Cannot remove ignition key from Picnic lock barrel

[Clive May]

The ignition key operates all the electrical functions, including starting the engine, but when I press in the key and turn it fully anti-clockwise, I cannot remove the key from the barrel.

I have tried squirting WD-40 into the key slot and jiggling the key while wiggling the steering wheel, but with no success.

To access the lock barrel I need to remove the plastic cover around the steering wheel. I have removed the single screw from the lower half of the cover, but don't know what to do next.

I assume that the upper and lower halves of the cover clip together, but I can't see how to separate them without damage being caused. 

I believe that once I get access to the barrel, I turn the key to the ACC (accessories) position, and then depress the barrel retaining catch with the point of a small screwdriver to enable the barrel to be withdrawn from its housing. I can then replace the lock barrel and fit a new ignition switch assembly to cure the problem.

Any helpful suggestion would be much appreciated.