Mine was wired by a local bloke who fits towbars at your house/workplace or wherever (Stoke on Trent/ North Staffs area). In the past I have always fitted my own but for health reasons did not do so this time.
In answer to your questions:-
1. Not sure, but I do know that he soldered wires into the loom just short of the connectors to the light clusters, non of the Scotchlock shite!!!
2. Think there may be plastic bungs or grommets underneath where the rear door pillars meet the floor as 7-core wires are fed in here I think.
3. There is not enough power available at the cig lighter/accessory socket. On my motor a suitably protected cable was run externally along the chassis and connected to the +VE battery terminal, an inline fuse was also used at the battery end.
The vehicle wiring is connected through a full by-pass relay and there is also a relay for the grey accessory socket both these relays were wired in, insulated and then slid inside the door pillars beneath the light clusters.
Using the by-pass relay has meant that there is little voltage/current drop and no extra loading is placed on the vehicle's wiring. I find that the lights seem brighter on both my caravan and trailer.
Berlingo Multispace 2.0HDI '54 reg Mediterranean Blue
you need access to both clusters, otherwise you won't have both indicators or side lights.
Main connections I did at passenger side cluster, and took a 2 core rubber flex from the drivers side cluster to the passenger side ( indicators and side lights ) cabletied along the top of the towbar.
Looking from underneath you will be able to see grommets under the rear door pillars (you'll need a torch, they are about 10" up into a recess ) i poked a hole in these to pass the wires through, take out the light clusters and as you poke the wire up it will appear, the relay I placed behind the plastic panel, opposite side to the jack (there's a hole behind the light cluster to get the wiring into the vehicle )
Power for the relay I took from the battery, going through a grommet in the bulkhead, then run inside under the plastic covers at the bottom of the doors, it's harder to explain than it is to do, you don't need to drill any holes.
Took me about 30 minutes to fit the towbar, and about an hour and a half to do the wiring, it was the first time I'd done towbar wiring so was quite impressed with my self, everything worked first time.
Anything else you get stuck with, give us a shout.
Somedays you're the pigeon, Somedays you're the statue.
thank you both very much for your help. Cheers.