Knowing nothing abut Leek moth I did a bit of Googling. One article said it is affecting mainly the south of Britain at present. None of the articles or illustrations look similar to your damage. As nobody seems to be sure what the trouble was (I still incline to spray damage) I would dig them all up and burn them. Dig the soil over thoroughly just in case there are eggs in the leeks. If you grow leeks next year and you are worried it might be the moth try covering the crop with fleece or a fine enough net for the adult moths to be unable to get through it. And don't grow them in the same place as this year.

Did this trouble happen fairly suddenly which could confirm the spray suggestion or was there a gradual deterioration?