Apologies if this is long but I've been having hair issues for years now and I thought I'd ask for help.
I had been having my hair bleached (blonde highlights mainly) for getting on for 25 years and over the last 5 or so of those had been trying in vain to get a more ashy blonde. It always seemed too yellow and despite using various toners my hairdresser could never seem to get that pale ashy blonde I was looking for.
Then 2 years ago or so the trend for silver/grey hair became a thing which I really liked. As I was 40 by then and my roots always seemed to be coming in grey anyway I decided to take the plunge and grow all my coloured hair out and go natural. In my mind I thought I would have naturally grey hair that would look gorgeous with no effort 
Fast forward 2 years, it's all grown out and the front and sides are a lovely silver but all the rest is just a boring mouse colour. I've kept it like this for a while but when I see pictures of myself I just don't like it at all, it's just too dark.
So I asked my hairdresser to lift the back and ends and colour them grey, so it would be a grey ombre effect, i could carry on growing out my own natural silver but the ends would be lighter and therefore silver/grey all over. I gave her the picture attached as an example.
What actually happened was that the ends and back have lightened but only to a yellow blonde again. She did it twice with 2 different bleaches but the grey toner just didn't hold.
I'm really disappointed and have resorted to colouring it all a pale blonde now to at least make it all the same but I still want to get it that lovely grey. It's so frustrating, especially as I spent so long growing out all the yellow and now it's just straight back again!
Can anyone recommend any products to get this colour? I probably just need to change hairdresser, but to give her credit she did use the exact same products she'd previously used on someone else who did get a good grey colour. Have I got the wrong type of hair?