I think if you are going for that floor (which is lovely) and pale cupboards then a darker worktop is a good idea, perhaps not black though. If you want for a deeper stone coloured cupboard then white or off white worktop would work well. That would be my choice. The light would bounce off the worktop and the cupboards a deeper warm colour would prevent it from looking insipid. https://www.floorsofstone.com/blog/a-perfect-partnership/

Thank you for the comments. I don't have any photos but the units will be quite pale, cooker is china blue. I was wondering whether Azzurite or Blue in the Night would work? Or I could just go with cream units and have a plain top. Floor is warm oak and walls/tiles not yet chosen.

I don't think the weight will be an issue as long as it is not a very finely supported island. If you require castors then make sure that the legs are straight not turned to a bun foot like your image. You need as much leg as possible to fix the castors. If you go for a 20mm thick marble or slate top you will not have a problem with weight or moving it. Get the castor type with brakes so that you can lock the position once you have the right spot for it.

Thanks Isla. He hand polished it all with Lithothin Stain Stop (https://www.protilertools.co.uk/product/lithofin-mn-stain-stop--choice-of-size-?gclid=CjwKCAiA8NKtBhBtEiwAq5aX2B_jSTe2vU64_eQh4-KEIs-IxvBdcXFP-pTwlXEYRXeLQR9lzUVz1hoCbcQQAvD_BwE) He had a mitred end panel and he machine polished that mitre edge but other than that no other machine polishing. When I asked if it only need hand polishing he said no polishing he does can contend with the polishing it comes with from the manufacturer. Would be amazing if that hazy, bitty film could go and look like it does in the first two pictures all the time.