Im 25 babe, honestly if you can get to Liverpool city centre in St John's precinct you should be able to pick up everything under one roof.
Its not a very classy place kinda like an indoor market haha but for the type of things you need you should get everything inc your tutu.
If you cant get a black tutu from there there is a lil place called Grand Central which has loads individual stalls inside. If there is not already a premade one in there there are loads of dress makers inside who will be able to rustle you one up in 30mins.