From here...
http://www.ivfconnections.com/qtransfer.htm
I think that your idea of “common misconceptions” is your own. Practices in the UK are not too much different than here. It doesn't make sense that in the UK there are a million embryos to be killed but in the US, there aren't.
Yes, the UK is different because they have government mandated requirements. In the US most fertility clinics abide by a self-governing set of rules. Clearly the woman who had six embryos transferred was not at one.
The couples I know who have done IVF have only had two transferred, at the doctor's recommendation. Some will do three if the woman is over 37 and the embryo quality is poor.