Ordered a pack from MB bearings on ebay of bushings and bearings that they said were right for my bike. The bushings look like little plastic things – is that right? I was expecting something more metallic…

Bushings are usually some kind of low friction polymer, so that sounds right to me.

Well, took it apart, the plastic bushings are in the frame, and then inside that is a steel pin with the bolt running through the middle holding it all together. The pin has a fair bit of wear. Put it all back together though and the play has gone, so seems ok so far.