Ants, how to get rid?

I've seen today a few ants around the edges of my poly, and was wondering how to get rid of them before they become a problem?

I was on my hands and knees trying to find the nest (or start of), but had no luck.

Is there anything I could use where they would take it to the nest and kill off the others?

my aunt makes a real fuss about ants -- powder everywhere, we even suspect one of her funny turns that lead to a fall was caused by overuse of flykiller in the house against ants.
So last year I took away all her stuff and I used bait boxes sold as ant traps from a webpage the professional pest controllers use (sorry I cant recall which) and also a rentokil bait box - within a week all were gone and none seen again all season. I am not a fan of powder as it lies exposed whereas bait boxes cannot be accessed by hedgehogs etc.
R

We use bait boxes at work to reduce the number of ants coming into the kitchens etc. Very effective. I think they come from Bayer