I use plain oatmeal (Tesco Value, in fact) and I either do it in a pan on the hob or in the microwave. Since I cook them with water, I imagine you could do it with boiling water as well- I'll have a go and see. I generally eat whole foods so I haven't tried any packets of porridgey things...
-------------------- "This is truly the age of bacteria: as it was in the beginning, is now and ever shall be."