Is it a gully of just 110mm drain?? Get your hand in with glove on clear as much as you can. If its old could be blocked all the way to the soakaway! Then you could excavate and dig back section by section to soakaway.
PlumbingAid, April 2010
put a hose pipe up from bottem turn the water on and see if moves any thing happens, plus you will get wet but keep going.