Dark blue-toned violet from dyed brown

Hi, everyone.

I wish to dye my hair a dark blue-toned violet and would love some feedback from you. I have a bit of box dye in my hair (L'oreal Préférence 3.21, a permanent dark cool brown dye) that is lighter at the crown (about a level 5 or 6) due to fading and lighter still at the roots where my natural colour is showing through (about a level 8 very ashy blonde). My hair is in rather good condition. I last dyed my hair in October, so the dye is faded a bit all over.

I have gone silver white from permanent black dye a couple times in the past, but it has been some years since I last did it. In my previous attempt I used Colour B4 first, which got me to a patchy dark ginger. While the Colour B4 did work (I bleached a couple times after doing it), I would rather avoid using it this time around as it's hard to get a hold of here and I had an allergic (not severe) reaction to the product.

My question is: How light would I have to go to get to the colour I want (I love the look of Adore African Violet)? I'm thinking of going for a less blue toned violet (maybe Adore Purple Rage) on the ends which now are more saturated in old box dye and will probably be harder to bleach light enough. I have used Special Effect Blue Violet on light gingery hair before with great results (in-between stage from black to white), but would like a more violet colour this time. I remember toning the ginger hair with diluted colour before adding the BV las time, so I might try doing the same thing this time too.

Please do let me know if you would like pictures of my hair as it is now.

Here are some pictures of similar colours to the result I would like to get: