I have also had yoghurts taken from me at the security posts at Heathrow, and so have many of my colleagues. Also, they won't let us bring in a tin of beans (more than 100ml), but if we empty the tin of beans into a tupperware container, then we
can bring that in!
If I go into M&S and buy some food, say a beef casserole, I can bring that in; but it contains gravy! How do they intend to seperate the gravy from the rest of the meal. They take yoghurts from me, but not trifles and creme caramels!
Over a period of a few days last summer, I took in a bottle of water. Every day the bottle got larger and larger, and eventually they stopped me. The following day I froze the water in the bottle, and when challenged at the check point I asked why. The said that I was carry liquids. So I challenged them, and asked for the supervisor to be called. After a slight 'discussion', I took my '1 litre bottle of ice' into work.
Having 'won' that one, I stopped doing it!
About 18 months ago, soon after they started getting silly, if they wanted to stop me taking anything through, I just left my entire bag with them! It's contains my wallet, my phone, my car keys, all my food and drink, my organiser, my house keys, my laptop (sometimes). It was always waiting for me on my return