I'm anxious to make this as soon as I can find corn cobs cheaper than $2 each! This is a preserve and while I'm more than happy to make the recipe as written, you might want to process it further in a water bath-something I can't advise you on.
Preheat oven to moderate 180c. Combine all vegetables, garlic and chili in a baking dish and toss with the oil. Bake for 30 minutes, then allow to cool.
In a large saucepan, combine vinegars, sugar, seeds and turmeric; bring slowly to the boil over a medium heat, stirring to dissolve the sugar.
Reduce the heat to low and stir in the vegetables. Simmer for 20-25 minutes stirring occasionally. In a small bowl, blend the cornflour into water and add to the mixture in the saucepan. Cook stirring for 4-5 minutes or until the mixture thickens. Spoon into hot, sterilised jars and seal immediately. Label and date when cool.