Where's Goldilocks?

Somebody's been eating my...butter. Okay, not quite butter, but some sort of margarine, or something like that. One of the "gruesome twosome," housemates S1 and M1, has been using my butter. I suspected this before, when I discovered crumbs in my last tub. I never leave crumbs in the tub. Then, I thought it was a one off. My prime suspect is S1, because the first time I discovered the crumbs was before M1 moved in. Recently, I opened a new tub. Last weekend, I was putting some of this butter/margarine/spread stuff in my jacket potatoes (baked potatoes for my American readers), when I noticed that there seemed to be a lot more missing than I can remember using. In fact, I am sure I only used this tub once, before. These days, I only put butter in my jacket potatoes. I don't eat any toast at home. I only put a small bit of butter in my potatoes, so there's no way I used that much. In addition, there were crumbs again. What cheek!
Why am I bothered about some butter? Partially, it's the principle. He's never asked me if he could have any, but just helped himself. Furthermore, I don't remember ever seeing any butter on his shelf in the fridge. That would seem to indicate that he is regularly using mine. He earns more money than me, so I don't think I should have to pay for his butter habit. It was different when a former housemate, Ray, would use stuff. He asked first and he often gave me stuff to return the favor. My Italian ex-housemate, Nando, used to ask first, as well. Also, I hate crumbs left in my butter. I feel like saying to him, "if you're going to steal my butter, can you please not leave your poxy crumbs in it?"
But it doesn't just end there. I now suspect someone's been using my shampoo. I have found my shampoo bottle turned upside down, a few times. At first, I thought someone might have just knocked it over and put it back upside down,by accident. When I found it upside down, the other day, I looked at the bottle, noting the shade where the level of the shampoo was in the bottle. It seemed like a lot was missing. It didn't seem like I could have used that much since I bought this bottle. Last month, my nail clippers disappeared from my toiletries bag, in the bathroom. They were imported from America. I questioned both S1 and M1, but both denied taking them. S1's girlfriend had been over that day, so I asked him if she had taken them. He denied this. A couple of days later, the clippers reappeared. This morning, I found my iron moved and left by the ironing board, that hasn't been put away for weeks. Someone's been using my iron. There are two other irons in the house, so there's no reason to use mine. Also this morning, the sink in the bathroom was covered in little black bits. At first I thought they were scratches, but then I noticed that they moved when I tried rubbing them. They were shaving residue! Hair that dark has to be S1, because M1 has blond hair. When I shave, I always make sure there is no residue left in the sink. The other day, I came home and found the TV left on, but nobody around watching it. The washing machine was empty this morning, but left turned on. I feel like Papa Bear, but there's no blond bitch around to make it up to me. Where's Goldilocks when you need her?