My daughter gave me two small plants earlier this year (her friend gave them to her!), and I grew them in a grow bag in a small poly lean-to with gardeners delight tomatoes, and they all had the same treatment. Tomatoes had less fruit than I normally get, but the tomatilloes grew like mad, producing loads of fruit and swamped the tomatoes!
The tomatilloes were mostly about 1.5" in diameter and looked quite weird when they turned purple and burst out of their skins. I've never grown them before, and won't again, but was worth the experiment. I gave them to my daughter about a month ago (her plan was to make the salsa dip,) and as far as I know they are still in her fridge! So all in all a wasted experiment really!
We had a very good summer here on the Norfolk coast, so maybe that helped, but it's tomatoes only again next year for me.