[Feature Request] Size of the row in Table Visualisation

I really need to be able to either add some more top & bottom padding to the cells or just height of the row

Good call. Definitely submit a feature request inside the product too: Feature requests and product ideas  |  Looker  |  Google Cloud Documentation

Have you tried messing with the HTML parameter? I know it’d be at the LookML level rather than the viz level, but could get you there in a pinch.