sohoradiolondon.com
Soho Radio in London seems like a similar thing to Le Mellotron. It's a little shopfront in Soho next to the primary school (yes there's a primary school in Soho). It used to just be a coffee shop with a DJ booth behind it but now hosts pop-ups for different labels - BBE, Wah Wah 45s, etc. in the front room, but through the glass even from the street you can still always see the live studio and whatever and whoever's on. They have regular shows from Shawn Lee, Jonathan More from Coldcut, lots of cool stuff going on there all the time. I like to walk by and spy on whoever's in there. I have no idea how they pay the rent.
nts.live
NTS is another streaming radio station out of East London - it's gotten a lot of mainstream attention and has had some big acts come on and do guest sets etc. It's kind of like... like a "cool office" will have probably BBC6 radio playing in its open plan area, but a "hipster office" will have NTS. That makes it sound kind of insufferable but there's been some very cool stuff on it. E.g. this mix of live dancehall recordings from cassettes:
https://www.nts.live/shows/death-is-not-the-end/episodes/death-is-not-the-end-26-08-17
I hope streams of actual radio stations isn't too off-topic. I like streaming college radio stations from back home:
kalx.berkeley.edu - UC Berkeley's station, home of legends like Billy Jam, Matthew Africa, too many to name...
kzsu.stanford.edu - Stanford's station, equally historic (Dollar Bin!)
http://kfjc.org/ KFJC.org - Foothill Junior College, yes! The dark horse of Bay Area radio stations, probably has the weirdest stuff overall. I remember a long running pirate themed kids show called Skull Time for Kids where the hosts would put on Long John Silver accents the whole time and never break character while playing childrens book records and shit. They do vinyl-only days, a "Day of Noise" which is exactly what you think, 24 hours of noise. 24 hours of James Brown May 3rd, appropriately called "Doin' It To Death". I'm unsure if they still do the Day of the Sun (Sun Ra tribute) but damn.
kpfa.org Berkeley free speech radio - Has two shows in particular I was always into - History of Funk still running after like at least two decades? Maybe more? And Negativland's late night live collage show Over The Edge, which has been running since 1981 and blew my mind about what samples could do when I was a wee hip hop head thinking Prince Paul was the pinnacle. It's insane they did this in the early 80s, it's kind of still insane to listen to now. It is a three hour freeform live sample collage performed on broadcast cart machines - like looped 8-track looking things, with live unscreened call-ins from nocturnal freaks with their own setups hooked to their phones.
Live radio, internet or not, is amazing to me when it's a non-commercial endeavor and it's just a handful of people and some basic equipment and a shitload of music filling 24 hours a day somehow. It's still magical to me in a way that podcasts and mp3 mixes aren't, even if you can micro-target your exact genre taste before clicking a mixcloud play button or whatever.