good points SK and Eco thank you. Looks like I'll be going with the flick tap, offset at 2pm to the right of the round vessel basin, mounted in the centre of the top of the vanity (not semi-recessed). Any thoughts on whether the vessel basin should be bang in the middle, or offset to the left slightly to balance the tap being on the right?

However, if you are just after looks, then the photos in your link, appear to have a 350mm basin which is leaving the 100+mm between front edge of vanity and basin. It does look better, but is that size basin too small for use?

The need to seal it attracted my attention because, while I don't know about that particular sealant and things might have improved, the issue of surfaces needing regular sealing is not very sustainably eco friendly and can have health implications. Do you know what solvent/s the sealant contains and what precautions are advised? The other question that comes to mind in relation to your actual question is, how vulnerable might the surface be as it's coming up to the time for resealing?

I’d have the biggest basin you can have without moving the plumbing. That may give space for two kids to clean their teeth at the same time in a pinch, and catch more splashes from washing hands under running water. Teenagers rarely put the plug in, so what extra functionality are you seeking by changing the basin? FWIW the taps don’t look centred under the mirror.