@smellypete this is the workflow i usually follow for models I know will be going on sketchfab.. avoid cycles, because you'll have to recreate all your materials and lighting in sketchfab..
I see your textures have loaded, thats good.
now for the wood material i usually use these settings:
I prefer tweaking the "Metalness" to the "Specular" but you can try either.
Ultimately i use "Roughness" to reduce the fidelity of the reflections..
and for metals i do this:
for these kinds of metals i reduce the "specular" and keep the rest the same..
for metals "roughness" is a great setting to play with, if you turn it down to zero you get chrome like highly reflective metals.. and adding something under 30 gives you a dulled metal look.. cranking it up will make it like brushed metal.
these are just my examples, feel free to experiment on your own as well.