Only place I've found so far: https://www.gameslore.com/acatalog/PR_Warhammer_40000_Conquest_LCG_Legions_Of_Death_Deluxe_Expansion.html

it'll be released this Thursday I'm sure if a retailer doesn't choose to sell their allotment early.

Yeah, but anyone lucky enough to live near Telford could get it this weekend