UK is saying today that the US may soon go on the "red list" with compulsory quarantine in a hotel (at your own expense, currently £1750) on arrival. So planning on flying to London, with or without global upgrades, may not be the best option....
If that's true, it won't be an option at all for most people in the US. My understanding is that only UK citizens and residents coming from red list countries are allowed to quarantine in the government hotel. Everyone else is banned completely.