I started out by trying to take the pin out, it was rusted in fairly solid but some hammering got it out. Now left with just the pin out the hitch wouldn't budge an inch. No play at all in it. I tried hitting the hitch over and over again with a sledge hammer with no luck, all I managed to do was hit it in about 20 mm so I could no longer get the pin in.
Tonight I decided to give it another go with the bottle jack and a hammer. Here are the results.
I was able to move the jack to certain point, then I would bash the hitch with the hammer. It would free the jack a bit and I would repeat the process.
Finally!