Thanks for all your replies! On how I discovered Libera, here's the longer (and more chronological) story:
While I was still in the school choir (about 6 years ago) we watched the movie
Les Choristes together. I didn't understand all of it at the time, but thought the songs in the movie were just beautiful. I found that the choir who sung them was "Les Petits Chanteurs de Saint-Marc", an excellent French choir (but at a completely different level to Libera as I'd later discover). I wasn't really a big fan the choir at the time, so I quickly forgot about them after a few days, until...
Some time in 2013 I found their album
Nos Rêves while fiddling with my dad's CD collection (more surprises in there later). He told me that they were basically the same choir as in the movie, so I played it from start to finish. This time they really got me in. I played it again and again, even trying to follow along with the lyrics in the booklet at times though I don't know any French. I started to think that they are one of the best among children's choirs.
Another couple of years after that I started using Spotify and the iTunes store (yep, I was quite slow into the digital age even though I'm
almost a millennial). By this time I've watched
Les Choristes again with my friends and I got deeply moved by both the story and the music. I bought all the songs in the movie from iTunes straight away, and then through listening to other albums of the choir on Spotify, I bought a few more of their songs.
This is the point when I hit You Were There.
I have to admit that many songs by "Les Petits Chanteurs de Saint-Marc" are of great quality and are still in my favourites, but their rendition (cover) of
You Were There was just rushed and not satisfying at all, so I started searching for other versions of it. The first result as you would expect was Libera's version, I clicked Play and never regretted it ever since. I was fascinated by the fact that it was a "bespoke" song made just for them (so arguably no other choir/group could have done it better). After listening to Libera's other songs for a while, I found that they have all the things about a good choir I was looking for: voice quality, coherence between different parts, the unique harmonies and the atmospheric accompaniment. Compared to PCSM, where Libera stands out is their focus on general singing technique and the relationship between parts, bringing the best out of every chorister, rather than just specific voices/soloists as in the case of PCSM (so when PCSM gets new soloists they sound completely different). On top of that their choice of recording equipment also make individual voices stand out more in a group performance, while not hindering with the overall sound of the group. Soon enough it was clear that unlike other groups, I will never get enough of Libera.
And that's how it all started.
I'd also like to take this opportunity to say that my listening habits are probably different from some of yours. The process is usually: Listen to music broadly on Spotify → discover songs/pieces I like → add them to my Spotify library → listen to the songs in my library → decide which ones out of those are my favourites → add them to my iTunes "Wish List" → listen (on Spotify) to the songs in the Wish List → decide which ones are the best out of those → click Libera's iTunes affiliate link → buy the ones I chose. iTunes has a few advantages: it is relatively cheap (paying per song compared to buying entire CDs or paying per month for Spotify premium); it doesn't occupy physical space (which is quite crucial for students); it is DRM-free; I can listen to the songs I bought in any order, without ads and offline (I travel a lot and often need music to calm myself down, and Spotify isn't fit for this purpose).
Perhaps you can say that songs in my iTunes library are my favourites, so the Libera songs I bought on iTunes are:
Angel (Single)
From "Angels Sing - Libera in America":
Wayfaring Stranger and
The Prayer
From "Eternal":
You Were There and
Ave Maria (Caccini)
From "Hope":
Salve Regina,
Dreaming of Home,
Stabat Mater,
Benedictus Deus,
From a Distance,
Three Ravens and
Venite Adoremus
From "Jupiter":
Home
From "The Christmas Album":
Once in Royal David's City (but a few other songs from this album are in my wish list)
From "Peace":
Gaelic Blessing (Deep Peace)
From "Song of Life" (should have bought them from their original albums):
Abide with me and
I vow to thee my country
These aren't my only favourites though - as I've mentioned quite a few songs are sitting in my wish list because it's so hard to decide between them which ones to buy!
If I
have to choose a singular favourite song, it would be "Benedictus Deus" because in my opinion its range, harmonies, variations, complexity and difficulty just describes what Libera is.
Also, the album "Eternal" is a special case - earlier this year (after buying the two songs from iTunes) I found the CD on my dad's CD shelf, along with the "Angel Voices - Libera in concert" (2007) DVD, so I just imported the CD into my iTunes library and now I have the entire album.
Oh and lastly, how could I have forgotten to mention my most important interest of all - fiddling with computers (aka computer science/cybersecurity/cryptography), because how would I be doing it at uni otherwise?
OK that's enough for now.
. Now I'm finally feeling the urge to join after buying my ticket for the Christmas concert which will be my first Libera concert. Hope to see many of you there! 
to write a concert review here. Jokes aside, it is so much fun to read the first experiences of fans such as yourself attending a Libera concert. 
Don't expect it to be very long though, as I'm not that good at using fancy words. 
And not using fancy words may even be a benefit for me because I'm not a native speaker.
