Thanks for the answer!
When i took off the bumber off, right beside the horn, there was a cable zip tied and tucked away. Is this the one you mean? couldn't find anything more, looked on both sides to be sure. i tried connecting the loose cable i found to one of the light bulbs i have (hb4 bulb), do i even have the right bulb?
First you need the correct bumper loom.
Your car has a loom with two wires which goes to the external temperature sender at the centre of the bumper. Looks exactly like this...
https://www.ebay.co.uk/itm/Vauxhall-Omega-Z22XE-1999-2003-Air-Temperature-Sensor-Wiring-Loom-09146829-/332216064602The other end goes to a four pin connector literally just above the horn.
Un plug this wire and discard it. Plug in the replacement bumper loom with four wires.
This should have two plugs for the fog lights and another plug for the temperature sensor.
I originally presumed that you had the fog lights and the wiring loom. If you haven't got the loom then someone here might sell you one if you ask nicely.
Also make sure that you have the correct lamps as the ones from 2001-2004 are different to 1993-2000.