Los Chimpos Ride Again

You think about the note.

'Amber nectar' clearly refers to beer, you presume, so you look over the last part of the note again.

What would a 'celestial orchestra' need?
You frown, and think about what musical instruments are in an orchestra.
Violins, flutes, all that stuff. What has that go to do with cele... wait!
You sit up straight.
Harps!
A celestial orchestra would need a harp!

And there is a pub you know of called The Harp where you can get the old 'amber nectar'... and that pub is by Covent Garden!
That's it!
It all makes sense!
The celestial harps, the horticultural gardens, and the beer!
It's The Harp pub at Covent Garden!

When in doubt, you think, go to the pub!