I had really light blonde hair for years then decided to dye it brown then black which I'm regretting very much,my hair is quite brittle and fine so don't want to risk bleaching it but I really want to go back to been blonde again,the hairdresser won't do it because of the condition of my hair. Please help!

At this point if your hair is that brittle I'm glad your hairdresser won't touch it as your hair would need to be first stripped of all the black color using a strong bleach. This is essentially a two step process. First strip out ALL hair color which is very hard on your hair. And then dye your hair blonde which again requires more bleach and toner.

You need to get your hair back into shape before attempting anything like you propose. I have been using for many years a Loreal product you can buy at any beauty supply store that should do the trick for you to get your hair back in shape and not be brittle any more. It's Loreal Nature's Therapy. Use that for a month or so and you should be able to have the double process done to your hair. My hair is the lightest blonde Loreal offers. I use this conditioner every time I shampoo and I get many compliments on my long, beautifully shiny blonde hair all the time (it's halfway down my back). The conditioner also gives your hair some nice body as well. My hair, too, is fine.