John Rumm wrote:

Can't speak for free.uk.diy.home, but the convention in uk.d-i-y (its
too old to have a proper charter) is that explicit adds are not allowed.
However if there is a genuine question to which you believe your product
might help, you can mention it. It is also accepted by most if you
include a link to your business site in your signature lines.

No charter for uk.d-i-y, but advertising policy is in the FAQ:
http://www.diyfaq.org.uk/#can

--
Andy