I play piano, never done any grades though but was at a fairly high standard near the end of school. Have fallen out of practice whilst at university because there's not really much opportunity for a pianist unless you're really good.
I'm also a brass player, having been taught French horn from year 9 until the end of sixth form. At university, I then branched out into other brass instruments in the brass band (they're all functionally the same really, except trombone): started with trumpet before being "encouraged" to get the correct instrument for the part (a cornet), then moved on to baritone due to someone needing to play the part! I remained playing French horn in the wind band.
I also sing (chorally, I'm not a soloist!), and participated in several different vocal ensembles both at school and university. I'm a bass, but have spent pretty much my entire singing career on tenor due to a perennial lack of tenors and the fact that I can just about get away with it...
University is possibly the best place to develop as a musician, especially if, like me, you aren't doing a music degree (though of course this does depend on the university, fortunately the music offering where I went is one of the best in the country). You meet so many different people, and it opens doors to various things you wouldn't necessarily have expected. Having now graduated, I need to find some way to keep up with music. Probably a local brass band.