Are there any recognized good brands for a liquid sealant for sealing the sump back to the block?

To be used on a Honda S2000 engine

Most manufacturers specify their own sealants, they are not expensive, at least you can be sure they are completely compatible and tested.

Halfords sell one from Loctite which is what I used comes in a pressurised can and it squeezes out nicely when you pull the trigger, makes the job very easy link