Towbar for Peugeot Boxer - Fiat Ducato (2013)

I am going ahead with this myself.  No issues for the towbar itself but fitting the electrics is not so well defined.  If anyone has done this job, or has seen how a professional has done it, I would welcome some information.
(1) The bypass relay needs to be wired in, typically (on other vehicles like my Vito) on the left.  But it looks to me like the wiring for the RH indicator is only available on the right, and the LH indicator wiring only on the left.  So I will need to run a wire from RH indicator to LHS up over the top or underneath.  Is this correct?
(2) What is the best routing to get +12v to the bypass relay and the 13-pin plug.  I need 20A or 25A; so am wondering what is the best place to find it, and the best route to get it to the back.  Of course, I want to drill as few holes as possible.
Thanks!

Recently fitted and wired y towbar to my 2012 duo (boxer)
 
I had to enquire about the wiring colours and got this useful response from Gram

Left Cluster
Side   Yellow/Green
Indicator   Pink/Blue
Brake    Green/Black
Reversing    White/Green
Fog    Brown/Black

Right Cluster
Side    Yellow
Indicator    Pink
Brake    Green
Reverse    White/Red
Fog    Brown

The Peugeot is likely to be the same.

Please don't 100% rely on this - it could be incorrect!

Gram
 
This was my post
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There are a couple of rubber bungs under the van below the light clusters giving access without any drilling. I fitted the relay on the off side and routed the two n/s wires underneath securing them with cable ties.
The 12v power I took directly from the van (starter) battery via a fuse. I again routed this underneath painstakingly threading the wire through existing cable and pipe mounting cleats. Mainly down the n/s. the trickiest / untidiest section was to the rear of the back axle.
The job is a bit of a faff, as there is not much room behind the light clusters but much cheaper and more satisfying than paying someone.
I did managed to get two wires wrong before I tested it so double check before sealing things up securely.
 

Hope this helps. 

When I installed my tow bar the 12v supply was picked up from the back of the 12v (cigarette lighter type) socket on the panel covering the offside rear light assembly.

Thanks for the info and advice.

I did find my wires to be a little different: I have added what mine after =>.
The
Left Cluster
Side   Yellow/Green
Indicator   Pink/Blue => White/Blue (could be my eyesight...)
Brake    Green/Black
Reversing    White/Green
Fog    Brown/Black

Right Cluster
Side    Yellow => Yellow/Grey
Indicator    Pink => Blue/Black
Brake    Green
Reverse    White/Red => Grey/Green
Fog    Brown.

I found the bungs - or in my case bung as I guess Autosleeper had forgotten to put back the LHS one!  RHS was the obvious side for the relays etc on the Symbol - the access holes on the N/S are in the shower and pretty small.
I decided to take the wire from Left to Right over the top.  This was a bit tricky to feed through but I used some 1.0mm T&E as a pull tape, feeding it in from the third brake light hole downwards.
I also found (just before I got your post) that the EM40 interface unit (=little fuse box)  near the leisure battery has fuses called Towing and Towing D+ which are permanent live and live when engine is running respectively.  So these will do nicely for powering the relay and providing the 12V supply that I need for the 13pin socket that I am using.  There is a socket on the back of this module (Tyco Mate-N-Lock 3-way) and I got the mating connector from ebay - arrived overnight!  I haven't worked out a professional way to get those wires down under the vehicle - it is possible to push them down alongside water pipes that go through the floor, I may have to settle for that.
So I am nearly done with the electrics.  Yes it is a faff - but the cost of less that £300 (includes Westfalia detachable hitch tow-bar) compares well with quotes I got for over a grand - and not much under a grand for an ordinary tow-bar.  And I know it is done properly, and I know where all the wires are should anything go wrong in the future.