Thanks to everyone for their suggestions. I have to say the leadwork looks really nice. Very neat – and probably even better after Hammerite. The sort of thing I would have rushed to do as a teenager. 🙂
Am kind of leaning toward the Olympic weights though. I wondered about stainless versions but they are more expensive – as you might expect. So something cast iron seems the best bet with an extra coating of paint and possibly one of these (see below) araldited to the inside to avoid it shaking about + velcro as Robin suggested.
A shame that no astro engineering company offers lathed rings to allow the conversion of weights for Paramounts and other makes.