I need to know how to colour my hair back to a warm brown from bleached hair? Using supermarket colours, I know they can be unpredictable...

I went from blonde to medium brown using a drugstore or supermarket color. And it turned out really nice. My suggestion 1st and foremost, would be to start using a semi-permanent color. Clairol Natural Instincts is a good brand. I used Hazelnut which is a neutral medium brown, and I really liked the results. There is also Cinnamon Stick, which is a warm medium brown (it will give your hair a reddish hue). If you have some gray hair, it will blend it nicely. Remember, it is a semi-permanent color which is actually good because you won't be necessarily stuck with the color if you don't like the change. Plus, you will need to re-do the color every 3-4 weeks, depending on how fast it fades.
Good luck!