I hooked up an air-ratchet to my compressor but it didn't have enough grunt to get it off. I had a go with the breaker bar but it didn't feel like I was getting anywhere and I was hesitant to keep going in fear of damaging it.

I'll pick up a proper rattle gun at Bunnings over the weekend and give it another go otherwise I might have to take you up on that offer Marshy - I'll bring some tyres over with me and try kill multiple birds with minimal stones.

Thanks guys!