Somebody has to be first to raise the topic here with the inevitable question - what's the anticipated fall-out for both property owners and ex-pats - if any

Far too early to say. It all depends upon what sort of deal the UK negotiates with the EU and what separate agreements will remain in force between the UK and Portugal.
Clearly the poorer exchange rate has an immediate adverse effect for may people.

Maybe Europe will do well regarding tourist as I cant see many Brits going to the USA with the way the pound has fallen against the dollar?