I've tried varying the ratio of oats/milk/water, cooking slowly on the hob (at least 15-20 mins), cooking in the microwave, soaking the oats first, making sure I stir the entire time but the porridge still doesn't thicken up and I'm left with oats swimming in liquid, rather than them combining together.
I've been making porridge regularly for about two years and usually use Tesco/Sainsbury's oats, so I'm definitely blaming the ingredients and not the chef!