I don't think that any of them are low in syns but I have found these and I suppose if they make 2 portions they don't work out too bad! I make my own version of "curry in a hurry" and there's no syns in it! Hope this helps!
Asda Balti Curry Cooking Sauce, Medium, jar, 320g jar 13 syns
Sainsbury's Taste the Difference, Thai Green Curry Cooking Sauce, jar, 350g jar 15 syns
Sainsbury's Taste the Difference, Thai Red Curry Cooking Sauce, jar, 350g jar 16 syns
Asda Smartprice, Curry Cooking Sauce, jar, 440g jar 17 syns
Marks & Spencer Red Thai Curry Cooking Sauce, jar, 350g jar 17½ syns
Sharwood's Thai Cooking Sauce, Yellow Curry, jar, 410g jar 17½ syns