Can't really comment too much because my DRLs were already fitted when I got my 2012 C1. However, the front fog lamps were not. I was able to get the bits of hardware necessary (lamp units, a relay and a new indicator stalk) but the wiring was already done. The bits just needed to be fitted (basically, attached and plugged in) and the bits all came with the necessary screws etc. So I'd say that there was a good chance that you might be able to just buy the right bits and plug them in - unless whoever fitted the after-market units chopped things around a bit (like, I dunno, re-soldered wires/connectors or cut the plastic housing or whatever).
I have had my bumper off but I wasn't particularly interested in looking at the DRLs at the time. I don't remember anything particularly surprising about what they looked like behind the bumper though.
It's probably not of much interest to you, but here's the thread detailing my adventures in fog lamp research:
viewtopic.php?f=3&t=10799