What to do!

I am so indecisive... but now I know for certain what I want. Blonde hair.

I'm naturally blonde... what shade I don't know because I've been dying my hair for the past 3 years... I think it's 'dirty' blonde from the roots I get. Anyway. So as I said I've been dying my hair for the past 3 years... I've been all the colours of the rainbow... the most recent was black... which I got fed up of.

So I had about 3 inches of blonde [dirty] roots and I thought I'll try dying my hair bright blonde... and yeah.. it kinda worked. I used Schwartzkopf Live [dunno how to spell that properly sorry]. Problem is... at the end it's quite a light shade of blonde... verging on platinum but not quite... more yellow... I wanted a more platinum shade but anyway... and so are the roots colour. In between I have different shades of brown and ginger. It looks okayish... but I really want my hair to be the same colour ALL over. Is this achievable without having to wait for my hair to grow much longer?