ABS Plug - Cannot remove top

I have eventually had another go at getting the TPMS wire through the bulkhead of my Octavia FL and have found the grommet that everybody said was there but that I could not see

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So I now have the wire in the engine bay and I have another problem.

The ABS plug has a lever that through some gears moves the big black lever and releases the plug (it took me a while to realise this as I could not understand what the Red locking lever was for). I have removed the plug started raining hard so I have re-assembled everything for the time being.

The plug is like in the photo but mine has a groove at the end opposite the cable entry and the side view looks slightly different.

Has anybody opened up one of these plugs?

Richard