To find asking prices versus sold prices without bookmarking a ton of stuff. Good to also see which agents are overpricing.
Google the EA and area + Getagent
Knight Frank Chelsea Getagent
Click on the first link google gives you: reviews and performance
Scroll past all of the reviews performance stats and activity and more agents until you get to:
SOLD PROPERTIES
Which you can click 'more' on until your heart's content - see screenshot.
Caveats: it won't be helpful if the home was listed with another agent then moved, you'll never know what the original full asking price is
I find the timings they state to be a bit inaccurate.
They must be dragging data from both Rightmove and the Land Registry.