The center post is a strange arrangement. The lower piece is internally threaded and the upper piece is like a bolt with a shroud around it. On the MC adapter the center post has a threaded end that screws into the lower section. The replacement piece I bought isn't threaded and just sits in the hole.
When fitted the MC adapter is very high, so as one of the many modifications I've made to it, I chopped a removable section out of the base pillar to lower the top when using the MC part.
I also bought a decent tyre lever, as the one provided will mess up the wheel, so budget an extra £60 for that.
I only tried changing one tyre with levers on the floor and that put me off for life. Using this tool makes it really easy. First one took about 2 hours, but most of that was about learning the tricks(and mistakes). I can now change a tyre in under 30 mins without raising a sweat.
Blowing up the rear can be a pain, as Darrsi pointed out, but you can get around this if you have a decent workshop compressor, firing an unrestricted blast in from the side rather than through the valve. Fitters do a similar thing, but have a dedicated small tank and nozzle to do it, but I achieved the same with a bit of hose pipe direct from the drain outlet.