HELP - brassy balayage disaster

[AuntPol]

I'm just back from the hairdresser. I asked for my usual balayage, caramel type colour (I have light brown hair naturally). This time around I don't know what she did different, but it's come out v light and yellow.

I don't have time this week to go back to the hairdresser - how do I fix it at home? I think I need a toner, don't I? - can anyone point me in the right direction of something I can buy from boots/Amazon?

Grrr. Hairdressers. Am thinking I need to stop using the local salon and cough up for a London salon instead when it comes to colour

[FrenchLavender]

Yes, toner but it will keep fading back to the horrid yellow. I sympathise, I had the same thing happen to me and it was hideous. It's taken me a year to get rid of it.

[AuntPol]

a YEAR?

I'm really pissed off now! Especially as it just cost me ££££ to look like this. Why is it so hard for hairdressers to get this right?!