Bleach Bath Or 9% Bleach and Powder?

I would never use 9%/30 vol peroxide when bleaching previously bleached hair, especially hair that is already blonde.
Can you get lower vol peroxide?
I would also start by using a colour remover (Colour B4 etc) to get the old permanent tint out.
Then you can either bleach your roots with straight bleach and add shampoo to the mix and apply to your darker areas in your lengths, or make two batches of bleach, a stronger one for your roots and a lower vol for your lengths.
Personally i would go for the second method as it gives you more control, but you will need to go through each section carefully so you will probably need an assistant.
I would probably use 20 vol for the roots and no higher than 10 on the lengths. You may need to process your roots for longer than the usual 20 minutes, but it will give you more time to correct the dark patches.
Try on a strand test first, and keep a note of the timings.

Your hair looks a little damaged in the pictures so i would really avoid any bleach or permanent dyes. Try a color remover, it might get the warm tones out of your hair and then try a blue toner ( no peroxide) that should get some of the orange tones out. And condition your hair after the remover as it might dry out the hair

Thank you for quick replies, my hair is only damaged at the ends where it is the colour I want, the rest looks bad because I commute on bike and it's unwashed 😀 I would never touch the ends, but the mid-lengths are only tinted, sorry to ask what is rob ably a stupid question, but do you regard that as bleached (I would say peroxide but just going by what the hairdresser has said)? The hairdresser assured me it wasn't, so I regard the orange toned mid lengths as OK to now bleach, the highlights I had once lifted this to a nicer colour so I know it will shift the warmth. I don't even know what a tint is, but it lifted my hair from natural colour to what you see there.

I can get 6%, but not confident this would lift my virgin roots. Was only planning on applying 9% for 10 minutes and watching it like a hawk. I'm not sure about colour before as the tint lightened my hair and I didn't think it deposited colour I could remove? Really confused about the tint, it was never explained to me and hairdresser was vague when asked and would;t take it to the colour I actually wanted. This is all such a faff, really mad at the original hairdresser, I had bleached my hair for years without incident until the ruined it and costs me hundreds trying to get back to my original colour.

A tint is a color dye which is mixed with peroxide. It is not the same as bleaching but the developer (peroxide) is the same and they both damage the hair. We call it processing.  I use 6% on my boyfriends hair which is almost black and it lightens to a light yellow in 30 minutes.

Permanent dyes bleach your hair just the same as bleach does, so don't assume that your lengths are healthy or unprocessed. There are slightly different chemicals involved, but it is the same chemical reaction that lifts the pigment out of your hair. The main difference is a tint (hairdresser term for permanent dye) has less lift and deposits colour, bleach just lifts.
I use 3% (10 vol) and a really good bleach powder (Matrix light master) to get my daughters dark blonde to platinum. I use 6% or less on my own roots and my hair is a darkish brown, level 3ish so much darker than yours, and it goes to a level 10 in around 40 minutes.

Aah that makes a lot of sense, thank you both. The tint did indeed itch and actually caused some scabbing on my scalp! I realised it had caused damage of course as it had lifted colour, so must involve processing. I understand it has caused some damage, but I feel the only area that will snap with further processing is the ends. But thank you for confirming the lower % would lift, that's great to know. I'll return the 9% for 6% and try an thick strand test 🙂