The Greek Billionaire’s Lair by Louise Rose-Innes

When Blair goes to Mykonos for a much-needed girls weekend she ends up having an impulsive one-night-stand with a mysterious Greek stranger. Imagine her mortification when she gets back to London and discovers he’s her new boss!
Kristos can’t believe it when the beautiful girl he bedded in the Greek Islands walks into his office. As his executive assistant, she’s determined not to continue what they started, but Kristos let her get away once, he’s not going to let it happen again.