Homebrew PCBs

Hi all,

I'm currently etching with Ammonium Persulfate, but having to heat it
up isn't very easy, so I want to give etching with hydrochloric acid +
hydrogen peroxide a go.

I've managed to get hold of the acid in the form of brick cleaner, it
doesn't specify the percentage, but I'm assuming it's somewhere around
30%, which seems to be standard.

The hydrogen peroxide however I had quite an issue getting hold of
(I'm in the UK), I've managed to get some medical grade (3%) stuff
from a local supermarket, however it mentions other extra contents on
the label, phosphoric acid & phenacetin. I'm not sure what the volume
of those additives are, as it doesn't mention it on the label. Would
they possibly cause an issue? I don't want it blowing up in my face
when I mix it :)

Finally, I've seen several mixes on the net -- with the medical grade
peroxide, does 2:1 peroxide:acid sound about right?

Many thanks,
Jamie