Page 4 on the info graph under "Supply Chain" it says that the majority of their products is through third-party brand partners. Selfridges do not directly source the products but curate them for their customers. Selfridges buying team purchases them from the partners or concession partners.

pg. 3

"Selfridges is more than a shop - it is a social centre powered by imagination, curiosity and creativity. We are part of a family of five brands including Selfridges in the UK, Brown Thomas and Arnotts in Ireland, Holt Renfrew in Canada, and de Bijenkorf in the Netherlands."