Originally Posted by
zen100
But I'm coming to the conclusion that I'm trying to do a tier point optimised itinerary - but all these Covid checks are just making it too risky

What's life (or TP running) without a little risk...
Get a PCR test at LAX on the 14th. I had one there recently and got the results under 2 hours, might have cost $125. The (minute) risk that the agent cares about the UK-Italy 48-hour rule (which you can't feasibly satisfy anyhow) isn't worth scrapping the trip.