Anything can be advertised as an 'Ugg' boot as an Ugg boot is the type of footwear that it is.
Thus New look, M&S and any other retailer could start selling 'UGG' boots.
The only way to tell whether it is the brand 'UGG' that you are looking for is to check the labels on the shoes.
I'd put my money on them not being what you think they are though.