jpsmit wrote:the bolt is correctly placed which is to say that when installed, the wide part of the bushing is on the inside of the metal and the narrower part is on the outside
Yes, that's correct, the wide part sits toward the inside of the car. That's what I have wrong on my Firenza - on that, I put the wide part so that it sits between the chassis rail and the subframe, which isn't correct, but it's a lot of fuss to do anything about it. One way to think of it is that on the original Vauxhall bushes, if the bolt rusted into the sleeve, it was just a case of undoing the nut (which sits on the outside of the chassis rail) and belting the end of the bolt, and that would usually push both bolt and bush out in one go.
As for the centre piece, I don't know, I thought all the poly bushes had steel centres, maybe that's only on stuff like wishbone bushes where there is an amount of rotation around the bolt on those. I guess the question is how much bigger is the hole than the bolt? If it's a good fit, then there's no room for a sleeve.