How to beat the london system with 1. ...d5?

I didn't know there was a refutation. I'm really only interested in a comfy position. I'm not expecting White to tip over in 20 moves anyway.

Easiest for black is an early c5, and take on d4.  Most lines will end up  equal.

The most aggresive lines with black involve an early Qb6, but both sides need to be booked up.

GM Pruess has shown aggressive lines for black (from about a year ago) that involve an early Qb6, or sometimes even Qa5 , but I couldn't find them (again) via Google.

There are no "refutations" per se, but GM Pruess plays the white side a lot, so he's would be expected to know the latest (and best) against what he plays.

That "info" is about a year or two old, FYI.  So the assessment may have already changed.

All those Qb6 lines with Bf5 sortie threats are good. But the question is what if white follows the seemingly more popular at amatuer level 2.Bf4?.

Infact I just played a game a few minutes ago as black against this sort of london. My opponent held Nf3 back and didn't have much trouble at all, until he made some serious position errors follwoed by a blunder.

2 Bf4 is actually the best move order for the pure london player, as advocated by GM Vlatko Kovacevik. indeed you can often do other useful things instead of Nf3.

the truth is, if your opponent plays the london you just have to accept that the position is going to be fairly dry for a little while...

I don't see what you guys are saying. 2.Bf4 doesn't stop black from going in the Qb6 lines. Just play 2...c5 and it will transpose.

If white takes you shouldn't have much trouble regaining the pawn, just play Nc6, e5, etc.

I think 2.Bf4 is fine if White wants to go for 2...c5 3.e4. Otherwise White has to deal with Qb6 stuff early.

well, an early Qb6 like in d4 d5 Bf4 c5 e3 Qb6 is trash, to say the least - 4 Nc3 and black's whole scheme has been pretty much rendered pointless. 3 e4 is also very interesting.

The best way  to stop Qb6 and Af5 is dilate Nf3

It might be helpful to look at Grandmaster Repertoire 11: Beating 1 d4 Sidelines by Boris Avrukh (2012).

https://web.archive.org/web/20140627001415/http://www.chesscafe.com/text/hansen164.pdf

Did someone bump this and then get muted or exterminated?

Looks that way.