Hi, eoghan.
I’m no expert, but I think you need to include a few maps. You may be able to get away with two: a map in the diffuse slot with the joint pattern and a bump map for the joints and irregular reflections. Make your reflective layer glossy, too. About 0.7-0.8 might be good. As for the HDRI, look into the dome light. The key to HDRI in my limited experience is the image you use. If you have more specific questions as you try things out, I’d be happy to continue to help, as I’m sure would others.
Cheers!