Under body / chassis pressure wash lance extension

[julianm]

Can anyone recommend something to use for cleaning the underside of the body/chassis? I see Karcher do a device on a little trolley which seems to give an upwards spray, but not seen it operating or had any feedback on if it`s any good. I`ve got a Nilfisk pressure washer which I`m very pleased with - can get into most of the wheelarch sections but it`s difficult to get right underneath, where lots of local road muck is getting plastered. Any ideas welcome - but I can`t really dig a pit!