How far north has the Leek Moth got?

I have been hit by Leek Moth for the first time this year in Nottingham and I wondered how far north they had spread.

At first I thought it was just wind and slug damage until I dug one up and found a caterpillar digging its way into the plant.

I looked up what to do about them and it seems the only option is to fleece the plants because nothing available to amateur growers will kill them off. I noticed that a number of people suggest cutting off the leaves but I think I have left it too late for the leeks to recover they seemed to go from quite healthy to slimy and poor in about a week.

I have dug up the whole crop, chopped them up and frozen them because its impossible to tell from the outside how deeply the grubs have dug. 

I'm very south and it's my second year of moth - why I didn't cover them this year I don't know 
Last year in November some idiots tried to steal my leeks by pulling them up, but the tops just broke off. They all regrew really nicely throughout the winter leaving the catapiller tunnels on their outermost leaves. So I've just been and cut the worst affected of mine down hoping they'll do the same as last year.

So far so good and no sign of them in Bradford.

Does anybody know anything about the lifecycle of this pest? Once we've got it (i.e. this year) are we going to get it every year unless we fleece?

Does it attack other plants (garlic, onions)?

Leek moth is specific to leeks, but Allium Leaf Miner is very similar in the damage it does, and that attacks all the onion family.
http://apps.rhs.org.uk/advicesearch/Profile.aspx?pid=652

and http://apps.rhs.org.uk/advicesearch/profile.aspx?PID=643

Not true. You need to go to specsavers. The RHS site that you quote says

"Tunnels in the stems of leeks and bulbs of onions, shallots and garlic"

Not true. You need to go to specsavers. The RHS site that you quote says

"Tunnels in the stems of leeks and bulbs of onions, shallots and garlic"

Don't need specsavers - I need to read the links first