Try this link :
http://www.brink.eu/download_manual.php?id=1156
it's a guide manual for fitting the hitch.
I fitted my hitch without any problems.
I'm not sure if the electrical connectors are the same for V70 and
850....

Link for fitting the wires .
http://www.brink.eu/download_kabelsetmanual.php?id=759041

In an earlier contribution to this discussion,

You should say where you are - because towbars may be different in different
countries. I assume from your address that you're in Australia? I know how
to fit a UK towbar, but yours may be different. However, it's likely to
involve removing the rear bumper in order to get at the ends of the chassis
members. ISTR that either the end bits of the bar itself or some threaded
plates have to be inserted into the ends of the chassis tubes. It's a long
time ago (1999) since I fitted a bar to my previous V70.
If the 850 bumper is similar to the V70, you have to drill out some rivets
where it attaches to the wheel-arch liner, and undo two large vertical bolts
which go up through the bumper's internal square aluminium tube. Then the
bumper just slides off rearwards (two person job!)