I've bought an advent calendar (Harrods). Rather than buy a 2nd calendar, I've spent the equivalent on eBay & Vinted to stock up on usuals: EGF serum, Good Genes, Happy Endings and AA Bath Oils.
I assume sales this early are by people deliberately splitting up their calendars and so (hope) not likely to have been tried. Have had more problem with clothing buys on Vinted than beauty.