I'm doing SW so a big syn free staple in recipes is fat free fromage frais or yoghurt.
I like eating this cold, especially in overnight oats, but I've never used it in recipes as I'm worried it will split or curdle.
Can anyone tell me if this happens when it's heated? If used as a sauce subsitute like in a fish pie, is it OK?

I have used it in a chicken and spinach balti. I used a low heat and it turned out really nicely. I think it is more likely to go wrong over a high heat. Not sure on the fish pie though, but I have read some people use quark as a substitute.

I don't know about the fish pie (I'm not a fan of it myself!) but I use it in curries etc. quite a bit.
The trick with using yoghurt/fromage frais is to put it into the sauce on the last minute. Take whatever you're cooking off the heat first, and then mix it in. That stops it curdling.

I've used fromage frais in cooking just fine x

I've used 0% fat yoghurt as a marinade for chicken with hit of tandoori spices, lemon and garlic. Marinade overnight then throw on hot griddle pan. Kind of a low fat alternative to buttermilk for tenderising. Makes great pita salad kebabs. Reserve bit of yoghurt and add garlic, chopped cucumber and mint etc as dressing with few hits of hot sauce and gerkins. Gah I miss eating meat sometimes

That sounds nice Paul!