What is the next strongest mould killer ("mold killer" to the
Americans) I can use?

The background to this is that I used some mould killer to stop
the mould in the grout between the ceramic tiles on my bathroom
wall. There is not much mould there at all and it only shows
black when the bathroom is damp from running a bath but I want to
stop it early.

I used "Polycell 3-in-1 Mould Killer". See
http://tinyurl.com/dngdb
It didn't seem all that great to me.

The label says it contains:
disodium octaborate (3%) and
benzalkonium chloride (1.5%).
The label also says "This product is approved under the Sale of
Pesticide Regulations 1986. HSE number 6157"

What is the next strongest mould cleaner to this one which I can
use in my bathroom?

And where can I get it from? (I don't want something I have to
obtain by the gallon and is only available from some obscure
wholesale chemicals warehouse!)


Zak