The title pretty much says it all. What instrument are you thinking of playing?
I want to do either flute or viola or a mixture of both if I can ^_^
There are plenty of orchestras to get involved in! For example you might be interested in Wind Orchestra or String Orchestra, as well as the larger Warwick Symphony Orchestra. You can explore a lot more of them here: http://www.warwicksu.com/societies/all/performance/