I have heard of a couple of crop dusting outfits in UK, but that was a while back and I don't even know if they are still in buisness.
On the other hand there are plenty in US and Canada. Work is very seasonal and very hard. If the sun is in the sky, then so are you. So you can forget any home or social life between May and September.
This is 2nd hand by the way, I'm not a crop duster but have spoken to quite a few out here on the praries.
Pay is around $1.00 per acre, and apparently a 1000 acres a day is do-able.
However, if the pylons don't get you, the chemicals will.
Good luck,
Sax