The fat free ones are usually labelled as about 0.1% fat. Sainsbury's and Tesco's have it under their "be good to yourself" and "healthy living" range. A good alternative is fat free natural greek style yogurt. To be honest it's practically the same, and the Total 0% one is very yummy, if a tad expensive. Look out for it reduced at the end of the day, as it will last about a week longer than that in the fridge.
If you use fromage frais as a soured cream alternative, beware that on chilli con carne and it will disintegrate into the sauce very quickly, whereas Quark will stay as it is unless you mix it in.