According to British Beauty Blogger:
"The MAC Giambattista Valli collection launches in July at Harvey Nichols, Harrods, Selfridges and Selfridges.com as well as maccosmetics.co.uk. They’re £17 each and the lip glaze is £19."
She doesn't say whether it's exclusive to them or whether Debenhams and HOF will get them later, but personally I'm fed up of the very high end stores getting exclusives on MAC. Very few people have Harvey Nichols, Harrods or Selfridges anywhere near to them, and the majority of the population don't live in London, so have to buy blind when this happens. I'm just glad I'm not interested in this particular collection, with the possible exception of the gloss.