Dear Kate,
I'm so sorry that you lost Alan's suit after all your hard work making it. And now I'll ask, are you sure it was moths? Moths make irregular holes anywhere from 1/2 inch to 1 inch wide, and more long than wide. Carpet beetles, on the other hand, make small, pin-sized holes, sometimes many in the same location. You can get them out with freezing or no pest strips if they still sell them in the UK. But as Olwyn Mary says, you're going to have to moth-proof the cupboard. We used alkyd paint in our historic garment closets in the museums that I worked in. It seems to repel both carpet beetles and moths. To determine what kind of critters we had, we put sticky traps on the floors. After a couple of days, we would examine the traps to determine how to treat.
Other things eat clothes, too. Crickets, silverfish to name a couple. You might check with your dry cleaner and see if there is a mothproofing solution it can use on your woolens so they won't attract creatures. And all the aromatic treatments are pretty much ineffective, especially if the clothing has been worn before it is put away.
I once spent several days restoring a "fancywork" pin cushion from circa 1880. It was beautiful, the top all beaded. It had been stuffed with reindeer hair, and my supervisor told me to leave it, rather than replace it with new stuffing. It was riddled with carpet beetles, and within a couple of days, they had eaten through the new backing I had put on it. We put it in a bag with no-pest strips (can't get them here anymore), and left it for several weeks. I then replaced the backing again, and it was OK.
I recently ordered a piece of deep blue wool for a new suit. It got carpet beetle damage. I know it happened here (at my daughter's house} because I examined it when it came andit was fine. So I'm in the same boat. Have to clean out the closet and get some mothproofing materials. All my wool sweaters are in there, and I don't know which are treated and which aren't.
Teri