Thanks for all the great replies and advice
Good luck with yours Tony - I hope the concrete cutting goes smoothly!
ChrisM - Thanks for the details and the pics, I might take you up on the "helpline" offer as I get more into the project. I figure also that by doing all the concrete at once the concrete from the pier might come spewing out the bottom, I'll use your method - thanks! I see you used 457mm dia tubing, I was planning on using 355mm - did you need the extra diameter for the steel pipe of was it worked out that pillars this high need that diameter?