Companion Plants

I'm not massively into companion planting. I think if you've got a garden full of everything then things tend to turn out okay.

The Enemy 

But when I look at my nasturtiums and see they're covered in caterpillars (and holes) and my brassicas have a lot less on them, I can see the benefits of having these companions plants in the garden

My nasturtium are looking a little holey now though

  Most of my nasturtiums are self set, and they come up everywhere. I tend to leave them in if they're in the corner of a bed and most of my sixteen beds have at least 2 plants growing in them. They look pretty, give me flowers for salads, seeds for "poor mans capers" and also attract the cabbage white butterfly away from my more useful plants.

The brassicas have plenty of holes but they'll survive!

Does anyone else grow many plants to lure the pests away from their main crops?