Hi Supernova - some of the halls at Leeds have practice rooms, ( Devonshire + one other? Can't remember) so you could start there - also the music dept has loads of bookable rooms - they will be full at certain times, but not always! I play the violin too, so you will hear me scraping away as well - if I get the (Biology - yes - this is the one that's the problem!) grades!
Also as far as I am aware, there are groups/orchs that you can/ don't need to audition for and some of them will be more serious than others, so go for it! See you in September.