i have the worst luck with my hair!

i know that there are probably a zillion other messages on this board about hair colouring disasters, but can i share mine and maybe you can help me?
it all started last year, when i got my hair highlighted at a hair dressers. i didn't like it, it was so bright and brassy so i managed to tone it down by using a hair colourant in ash. since it was the summer, though the sun didn't help with keeping the colour and it started to go red after a while. by the way, my natural hair colour is medium brown.
when i got back from my holidays, i decided to put my hair in the hands of another professional to get highlights in again, but this turned into disaster no. 2! he dyed my hair a really dark colour, and then highlighted it this really brassy colour with chunky highlights- totally not me! so i went back the next day, bravely and he dyed my hair to a colour close to my natural one.
after a while it started to fade so i used a semi permanent colourant at home, which i continued to use every 2 months to maintain the colour.
my mom persuaded me to try AGAIN for highlights a few weeks ago so i explained exactly what i wanted to my hairdresser- thin, subtle ash highlights where i wouldn't get dark roots. still, i wasn't happy with my highlights (although it was better than the last time) because there was still a lot of brassiness in it. a week after that i dyed my hair light ash brown and that seemed to take away most of the brassiness, but it didn't last long.
then my mom convinced me to highlight my hair at home, which turned out the nicest of all except in a few pieces which went brassy, but i managed to tone them down quickly by using the light ash brown colour. now, the highlights are the colour i want but i still have red and orange bits in my hair which get more noticable with every wash.

i use a toner (its usually really dark blue stuff) which helps a lot, but the chemist has stopped stocking this toner now when i need it the most! this toner only lasts about 3 shampoos as well and i would like a stronger one.
can anybody recommend anything for me?

thank you so much!

Wow...after almost 4 months no one had the decency to address these questions. Real nice...