I'm just in the process of writting a review at the moment. We visited last May, and really enjoyed it, even if it isn't going to top many best WHS lists. Having a car is all but essential.
We stayed one night Truro, which was a a nice surprise, nothing spectacular but rather charming and some excellent food. The second night we stayed between Plymouth and Tavistock, handy for heading into southern Devon and Dorset.
We only had a quick stop in Tavistock, it seemed nice, but not especially remarkable. Dartmoor national park next to it was lovely though. We were heading right down to Lands End (don't bother going that far for the Land End fairground though) so wanted to be further down the peninsula.
The stand-out location we visited was St Agnes
, which I think shows Cornwall at its best. There is a small mining museum, and a charming little beach with a surf life club, but the main mining sites are on the hills up above. This would be my must see from all the sites.
Also the open air meeting place at Gwenapp
was unique and a worth making the detour to see. And Chalrestown was one of the more photogenic locations, and had some mining related museums.
St Just has access to the mines, if that is what you wanted. But if you've ruled out heading that far not relavant.
I wouldn't put too much hope in Redruth or Hayle being highlights, they may look good on paper but reality isn't so great.
Outside of the WHS. Zennor was very pleasant, we had an excellent Sunday roast in the pub there. We ended up skipping St Ives, we had planned to visit but access to the city centre is closed to non resident cars, and it felt very very busy. So we decided not to battle the crowds, March may be a better time though. If you fancy visiting Newquay, be prepared to encounter more British drinking parties than Amsterdam, Prague and Tallinn combined.
Bristol is worth a bit of time as well. The Docks and SS Great Britain, as well as Temple Meads Station were all previously on the T-list. There is also the second branch of Stanford's
book shop. Their other store in London is perhaps my favourite shop in the world.