In a large mixing bowl, pour  in the bottle of chili sauce and brown sugar. To the almost empty bottle of chili sauce, add the Worcestershire sauce and vinegar. Screw the top on, and shake really well. Dump this into the bowl with the chili sauce and brown sugar. Whisk these together, breaking up any brown sugar lumps – you want a completely smooth sauce. Add the can of tomato sauce plus the mustard and whisk until combined. Store in an air-tight container for up to two weeks.