According to my LFS, and I quote as I was in there just...
"Siamese fighting fish are very peaceful fish and will get along with all other species"
Or something very similar....
They do say how males cannot go together, which i suppose is better than nothing. But they also say how they can live in small vases and even sell them, £9.99 for a vase about the size of a 2L bottle of coke, some betta food, with a bit of gravel in.
It's quite shameful really, but they sell a lot of betta's from what i can see, there always changing and the guy on the desk once told me they sell a lot.
So all i can hope is that they're going to good homes, with people who know a bit about them lol
This really being the reason i want to sell my fry privetly!