Pretty much nowhere can sub-ICAO aeroplanes (the international legal term for what USians call "Experimental" and Brits call "Permit") be used for commercial purposes, except usually instruction to fly those specific aeroplanes. That's not unique to the USA.
£1.65/litre AVGAS is a problem - MOGAS sipping Rotax engines, which also cost far less to buy and overhaul, do make a lot of sense, as will MOGAS STCs for Lycontinentals - we are already starting to see MOGAS pumps on some UK airfields.
There are certified Rotax and Jabiru engines, so this is a realistic option in the future for existing and new spamcans. Just because it hasn't been done much yet, doesn't mean that it can't. Also there's a future for AVTUR sipping Diesels in aeroplanes, we've seen them already and I'm sure we'll see more. AVTUR in the UK is similarly priced to anywhere else.
G