Hi,I am desperate for some advice please,but first I will tell you my colouring story!!
Ok my hair is naturally dark brown(with a little grey)I started having bleach blonde highlights around 5 years ago.My hair has gone from being very short to shoulder length and now shorter again.Well last Tuesday(4 days ago) my hairdresser arrived and I said I wanted my hair blonder I meant the colour, because the blond was brassy it was never white blonde enough,anyway after the colour, a very big trim and finish I looked in the mirror and OMG I was crying!!
I am nearly a full head blonde, she thought I meant more blonde not blonder!! My highlights are many colours, we have orangey coloured roots we have white bits and we have a lot of yellow all over.
Please help someone I really want to go back brown I am now sick of being blonde,but I can't afford salon prices will I be able to do this myself!! I really hope so :)
P.s My hair is very thick.

What you want to do is a "tintback". It's not trivial.

Basically, you get a haircoloring (single-process, most often a demi-permanent, to minimize damage) and dye it back. The big problem, however, is that if you do this without careful planning, your hair will turn out greenish! To avoid that, you need to add some red back into the hair first. (red is removed from your natural undertones when you bleach). That is often done using a red -dye. The process is called "filling the hair". Some people use reddish protein "fillers" to do this (that usually doesn't work as well as the dye).

Note that the color and the amount of red are very subjective. If you put in too much red, you'll be a redhead. If you pick a haircoloring that's the exact color that you want it to be, it'll almost certainly turn out too dark (bleached hair absorbs a lot of color). Furthermore, you will have problems with fading.

Quite honestly, I think you'll do better to try to get a dark blonde color.

For more information, I suggest you look and post here. There are a lot of coloring experts that have posted there.

Bottle Blondes Board (http://www.network54.com/Forum/503669/)
Or
The Going Blonde Message Board (http://www.network54.com/Forum/127834/)