Hi guys!
Thanks John, yes for the price it really was cheap
Another update now! It's all done! I widened my slab so it's now 0.4m^3 and I found Vicmix to have a very good price, it was ~$160 for the concrete. I also decided to pour the bolts in too rather than drilling. I made a template of the pier's holes on wood & some metal sheet and used them to keep the bolts aligned during the pour. I rested them on the rebar and used wooden blocks to level the rebar/bolts.
I know that the wooden blocks and metal sheet may disintegrate over time and leave cavities but I think the slab will hold up fine
now time to paint the pier and start imaging!