I just buy a large bag of value branded Tesco or Asda oats as I don't think there's much difference (if any) between those and the branded bags of oats.
1x small espresso type mug of oats, 1x water, 1x milk then microwave for 2 mins, take out and stir, then microwave for 30 seconds.
Take out and stir, add flavouring then enjoy.