I checked before ordering about the bumper and was confident I didn't need to remove it. There is a brace bar behind it and you need to be careful when drilling for sensors A & D as the drill will hit it when through (more so as not to snap the drill). The top of the rear bumper is just over 500mm but the sensors fitted easily at this height though they need to be eased home (the cutter supplied was perfect). It's a bit fiddly but the wires can be cabled tied to the brace bar.
I drilled a 10mm hole in the spare wheel housing (some trays have to be removed for this but the spare wheel can stay in , put in a grommet (bound the wires here with insulation tape) and cabled tied the sensor wires to the loom leading to the nearside rear lamp. There is a locker on the nearside which has an access panel made to measure for the . Removing the floor tray (2*self ) allows access under the side trim panel.
It is easier to remove the rear lamp (3*10mm nuts) to join the wires. They are not that thick a gauge wire and I opted to solder but scotch locks should do the job. Removing the lamp also makes it easier to feed the wires up behind the trim panel.
the bleeper was my only problem. It will fit in the locker but I carry several crates and have the cover over them; this does muffle the sound so I opted to run the lead up the trim and put the sensor on a rear window ledge where it's out of the way (for me) but probably not the best place; really depends on the installers preference.
Proof of the pudding was backing up and I'm relieved to say it worked first time (and every time since). the photo shows how close before the continuous tone (In reality this equates to a closer distance than the cone I was using).
All in all worth the money.