Hi! I'm one of the choral scholar ambassadors at Nottingham and the choirs that we have are: Viva Voce (auditioned), Coro Sorelle (unauditioned girls' choir), Man Choir (unauditioned male choir) and the main University Choir (unauditioned).
Viva Voce can be quite competitive for sopranos, but there is no fixed standard as such. The singers do tend to be grade 8 or above, however, and some are choral scholars and/or sing with NYCGB. But it's more about your ability to sight-read, and how well you actually sing.
The girls' choir, male choir and the University Choir are all very welcoming, and the music that they do sing is of a high standard - Uni Choir did the Durufle Requiem last year and there's talk of doing Britten's War Requiem next year. So it's not at all bad if you don't get into Viva in your first year.
Choral scholarships are available at three churches in Nottingham: St Barnabas Cathedral, St Mary's and St Peter's. They are paid, and have various perks for each one, but check out the websites for the churches for more info. You don't have to be a music student to have a scholarship though!
Hope that clears up everything!