The Shoe Size Lottery

I have read several magazine articles recently about the lottery that is clothing sizes. Does a UK12 equate to a Euro 38 (Oasis, H&M) or a Euro 40 (most other places)? And indeed, what is a UK12 as it can vary wildly from one store to another. I have clothes in my wardrobe ranging from a 10 to a 16, all of which fit me.
This got me to thinking about the variations in shoe size. Yesterday I went to a local independent bridal shop to find shoes for my sister’s wedding at which I am a bridesmaid, and tried on a shoe in a size 41. It almost fit. I am normally a size 42 or 43, depending on the style of the shoe. Note that I say 42 or 43. I used to say size 9 but depending where you are shopping, either a 42 or a 43 is classed as a 9. Consequently I can wear an 8 if it’s a ‘big’ 8 and is really a 42, and therefore almost a 9! It’s all very confusing. That there has to be 3 sizing methods in this country is bad enough (UK, Euro & US, which many designer styles are sized in), but it is made worse when stores can’t even agree what equates to what. On trip to New York 3 years ago I learned that I was a US11M which I believe equates to a UK9. However, in recent times I have purchased several pairs of shoes and boots by American designers (Nine West, Roberto Cavelli) and found myself to be a US10W, and on one occasion, a US9W which is meant to equate to a UK 7 but there’s no way I could ever wear a UK 7!
The very friendly and helpful lady in the bridal shop said it would be best to order a 42 which she kept referring to as a 9, and called the 43 a 10. As the 41 was only a little too short for me I agreed with her and she ordered the shoes for me. They are the style pictured which is called ‘Lily’ and is from the Pink range by Paradox of London. I am having them dyed a dark red to match my dress.