Our local drain specialist did the job for us for =A350. Waterproof
camera in a torpedo shaped case on a line with the image on a TV
screen. The line was much like black alkathene water pipe on a roll but
semi rigid and could be poked a long way like a drain rod.
Fascinating viewing with a very clear image of the pipe and it's
contents - bit like one of those coral reef nature films but with bits
of sweet corn, bog roll etc instead of fish. Talk about seeing crap on
the telly! Should have kept the video.
The result was that we found no main drain but a soakaway pit instead,
which accounts for the periodical blockage.

cheers

Jacob