Arriving back to LHR from LAX, mid afternoon in Upper Class, is there anywhere I can go to freshen up? I see the arrivals lounge will already be closed?
Yes Revivals closes at 1.30.
You could look at the Air Canada arrivals lounge which is on the priority pass scheme but I would imagine that would close around that time too.
You could try to get a day rate at one of the nearby hotels. I think the Yotel at T4 does those.
There are some airport showers but am not sure if these are in T3 or not - check the LHR website.