Some Demi's do have lower peroxide levels but those platinum ones are definately 40 vol. I used one of the new feria ones for platinum blonde to bleach my hair and I can assure you its 40 vol as I got a burning sensation on the nape of my neck where it touched the skin. I've only ever had that with 40 vol ones.
In one of Scott Cornwalls posts he said he did a test on various box dyes to check peroxide levels and that most had 30-40 vol.
So much info haha, but it's starting to all make sense to me. I tried to find what volumes l'oreal preference les blondissimes and excellence creme supreme blondes ultra light ash blonde had in it but I couldn't find it. In 2011 it was listed as 30 but idk if its still the same.
Many hair dye companies will not tell you what volume they use. I have heard of people calling the phone number on the box and they refused to tell what volume. It's safest to just mix it yourself. I know Feria is strong.
*nono* wow that seems sketchy. What would you guys suggest for golding out the bottom?
I know Glitterpix had great results warming up a pale blonde with Superdrug's honey blonde toner (you can see results here).
If you think that may still be too pale, look for a darker toner in the Superdrug line.