Reporting back on the sweet & sour - it was really good, although as usual a struggle with only 3 working hobs - I had to keep some components warm in the oven while cooking others. Prawns for Nate were battered and fried first then I put them to keep warm while I did my pork in the same oil - so there was no contamination of his meal.
OMG can I just say Iceland pork medallions from their fresh meat range (and part of their 3 for £8 deal - there are 4 in a pack and I was greedy and used 2, a pack would feed 4 in this dish with sides though) are perfect for this, I just sliced into thin strips and coated in a simple egg/cornflour batter and then fried for a few minutes and it turned out perfect melt in the mouth tender and a little crispy batter at the edges, will definitely do again.
I do the sauce 3:4 sugar:rice vinegar plus tomato puree or ketchup, thickened with 2 tablespoons of cornflower in a bit cold water then heated until it thickens. Splash of light soy sauce or sesame oil goes nicely but isn't strictly necessary.