Hi Stina,
That looks a good find. As it happens, the blue scrap car I've just collected also has a proper "bent" towbar on it.
The one I weighed in on Saturday had a "straight" one, but the front end looks very similar to the one you have there. I was surprised to find that it was bolted through the rear jacking point. My own car's towbar has two parallel front bracing irons, one running either side of the jacking point which is easier to fit, but perhaps not as strong.
The length of the loose bolts on yours do suggest that they pass through the jacking point which will need to be drilled first. Anyone know if this is the more common way of fitting them?
Anyway, this does mean that I probably have a suitable part to finish yours off which will save you making one up. I'll check when I get back this evening. (Tenner plus postage if it's compatible?)
For the wiring, if you unclip and peel back the trim on the right side of the boot, above the battery, you'll see the bullet connectors leading to the rear lights. You can connect in there without cutting anything. If you buy the above, I'll throw in the wiring from the blue car, but would still recommend you buy a new socket as old ones never work reliably.
I believe that it's now a legal requirement that new fitments need a buzzer or light on the dash to indicate that the trailer flashers are working. It's up to you whether you choose to argue that your car already had a towbar before this law came in, or figure out how to comply.