No masks, no testing, no reporting, no quarantine, the public have basically been told that it is all over -- now go back to normal.
Coincidentally we have also been told that currently 1 on every 20 people currently has the virus, and that it is ok to go back to work with it, if you feel well enough.
As far as hop on hop off buses, I don't believe that they work well in London, are very expensive and exceedingly slow.
If you want to see London from the top of a bus look at TfL's (Transport for London's) official website for all things transport in London. They even have a sort of best buses in London map which shows many of the places you go round. Granted, no multilingual taped disembodied voice telling you what you just passed, but sit upstairs at the front for a picture window view and follow Rick's book and the map.
https://content.tfl.gov.uk/bus-route-maps/key-bus-routes-in-central-london.pdf
And you can hop on and off from one to the other all day to your heart's content for only £4.95 (the daily bus only cap). Try doing that on any HoHo bus.