Fallout: London Official Release Trailer
I just received an email from GOG saying the mod is available for free there (you still need to own the FO4 base game). The "catch" to download from them is that you have to subscribe to their email advertising.
https://www.gog.com/en/game/fallout_london
Don't need to subscribe to anything, just need a GOG account. The mod is hosted on GOG because Nexus denied them due to size.
you apparently already subscribed to their email advertising
And then unsubscribe or block as soon as you've got it.
They're hosting this 33Gb download for free - I don't begrudge them trying to advertise a bit.