The situation: driving on the M25 and come across debris in the road. Easy
enough for me to avoid it but plenty of potential for an incident.

Should I have stopped and phoned 999 to report this, or is there a better
number to phone (like the Highways Agency)?

I thought at the the time phoning 999 wasn't called for as there wasn't an
accident. Although in hindsight, there was plenty of opportunity for one to
happen.

TBH, I don't even know if the H.A. have a number to call in cases like this
and I find any advice on their website.

So, 999 or H.A.? Advice please...

--
Regards,
Steve

"...which means he created the heaven and the earth... in the DARK! How good
is that?"