Dyeing my hair

[cest.la.vie]

[Pre-amble: I naturally have brown hair, and I've had a lot of blonde highlights done (my hairdresser is an idiot, I wanted a whole head colour but apparently 'no one had that done anymore' so she just did a lot of highlights).
As a result, to look at, my hair appears blonde on top, and just slightly darker underneath.]

So, I want to dye my whole head blonde, and seeing as my hairdresser doesn't listen to me, I've bought two bottle of hair dye. However, I'm not sure how it'll work given that part of my hair is bleached already...

Will it turn out relatively ok if I just leave it on longer on the parts that haven't already been bleached (the underneath where it's brown), and only leave it on the already-bleached parts/highlights for a short amount of time?

Sorry if that makes no sense. I don't care hugely if it goes wrong, I'd just prefer to avoid messing it up completely/doing something that's particularly hard to reverse.

[On the bottle it says 'don't use over pre-coloured hair blah blah', but I'm not one to listen to official intructions. Plus, I have two bottles of colour, and a bottle of brown floating about so I can attempt to fix it if it goes horribly wrong]

[Sans Peur]

When i bleach my hair i do the tips first and work my way to the roots and they go quicker.I am unsure how you would deal with the already highlighted part.have you ever done this before?

I would personally go to a hairdresser or atleast get a friend that has experience in this to help out as it can mess up and severly damage your hair

Jane x

[*phantom*]

If you put the bleach on the whole head,
it'll go lighter on the bits you've already had done,
which might make it look quite multi-tonal and pretty =D
but that prolly didn't help.
x

[cest.la.vie]

Thanks for the quick replies.
I've dyed my hair before, but not since it's been highlighted which is why I'm a bit unsure about it.
And she's highlighted my hair three times, so there's different shades of blonde... I'm confused to say the least!
I might do the 'strand test' thing. I just wanted to make sure that I wasn't going to do anything drastic, like turn the highlights green or something.
But if it just goes multi tonal, then that would be quite cool :)