... You can get a Curvy Kate Multiway Plunge bra for £6 in the asos sale.
www.asos.com/Curvy-Kate/Curvy-Kate-D-J-Desire-Multiway-Plunge-Bra/Prod/pgeproduct.aspx?iid=2851083&cid=8146&sh=0&pge=1&pgesize=36&sort=3&clr=Ivory
I'm not a 30J, but I do know how expensive bigger bras are so I thought I'd link to this.