Hey, I think I have just done exactly or pretty much what you did in 2014! I decided to chop my hair off, go "lilac" via my hairdresser (who did achieve lavender/lilac) and then after one wash it was a faded lavender/pink.
In my stupidity, after the first wash, I decided to use "crazy colour" in lilac TWICE to get the colour back. I am now BLUE/GREY!!!
My hairdresser hasn't replied to my calls for help (probably thinking it's your own fault, you deal with it, although she did recommend crazy colour...) and I'm freaking out I have this weird colour hair!
Did you manage to get it Sorted and if so, how? X