To answer the original question mine is the original Pollak 2 blade style and it takes a 7/8" deep socket to remove it. there is a gasket around it that may not come with a new switch.
Thanks! I somehow missed your message earlier. I used a 23mm socket so 7/8" is probably the correct size. Turned out that a deep socket was too tall to fit in there with a ratched so I ended up having to make a custom socket from a cut off box end of a spanner, piece of pipe and a nut in the other end so I could turn it with another spanner.
I opened up the old switch and it was burned up from the contact points. If anyone else has this issue then you could try turning the plastic connector part just a few degrees so the contact points change. It might fix it, or it might snap off and now you have a broken AND oil leaking switch...
Oh and good call with the gasket. I would have left mine sitting of top of the transmission if you didn't mention it.