Hi Sarah
Yes the moth is everywhere around here this year and I was shocked to discover quite a bit of damage last week, on quite large leeks.
However the season is drawing on and the moths should finish eating soon, before pupating. So it may be best to leave the leeks and let them recover once they become pest free in October. Late varieties such as Apollo, Bandit, Edison and Musselburgh will do better because they are extremely hardy and able to grow strongly in any mild weather throughout the winter and early spring.