I managed to cook pork chops successfully tonight! They weren't tough at all! I made a marinade of lemon juice, chilli and garlic flakes and olive oil and left them in it all afternoon, then cooked them in the oven with roast potatoes, roast parsnips and carrots! They were defrosting while they were in the marinade as well, so I don't know if that made a difference. Anyway, thank you for all your tips, something seems to be rubbing off!