You haven't mentioned what variant of i30 you have, whether it's the FD (2007-2012), GD (2012-2017), or PD (2017 onwards). I've fitted towbars on FD and GD hatchbacks. The FD did require cutting notch out of the rear bumper and I think I may have had to remove it completely. If you go on the manufacturer website you should be able to download the fitting instructions so you know what's involved. Those tapped holes under the car may be bunged up by rust and dirt which makes it hard to insert the bolts supplied with the towbar, I suggest if the bolts don't go in easily, get a tap and run it through the holes to clean up the threads. I think they're M10 fine pitch, not standard pitch like you find in cheap tap sets. When I did mine there was a mechanic in the unit next to where I worked and he lent me a tap to do it with. Make sure all the bolts go in easily before trying to lift the towbar into position.
On my GD there's a plastic undertray at the rear I had to remove. On one side, two of the towbar fixing points are used to hold a bracket with a tie-down point, so that bracket has to be removed completely in order to fit the towbar. As I recall, I had to cut away some of the undertray to fit around the towbar.
When lifting the towbar into position, push screwdrivers into a couple of the mounting holes to take some of the weight, whilst fitting the bolts in the other holes. Once they're in position to take the weight, pull the screwdrivers out and fit the remaining bolts. Bear in mind the bracket is quite heavy, especially if you're on your own with the rear wheels up on ramps. Needless to say, DON'T get under the car if it's only supported by jacks.
I don't know what the wiring kit is like, is it one of these that has plugs and sockets that connect straight to the car wiring loom (plug n play) or do you have to break into the existing wires? I just used a universal bypass relay which has a terminal strip for the towbar socket, and a flying lead of wires to connect to the car wiring. I mounted my relay behind the trim inside the boot, and drilled a hole through the spare wheel well making sure the cable from the socket reached to the relay.
The relay needs a +12V connection, on my GD I picked it up from the 12V socket in the boot. On the FD I had to run a wire all the way to the fuseboard by the drivers' knee, which meant threading it under the carpets. I used a fuseholder with a flying lead so it just plugs into an unused fuse position.
Neither car had CAN bus to the rear light clusters, so I could connect to the existing wiring, once I figured out which wire went to which bulbs. I used butt-splice crimps instead of the scotchlock connectors. I cut the wire, stripped the end and twisted it together with the wire from the relay, and crimped it into one side of the crimp. I stripped the other side of the cut wire, doubled it over and crimped it into the other side of the splice. I already had a crimp tool.
I did publish some photos and notes on the forum about 5 years ago, but they're only relevant if your car is a GD.
