Hi Gents, is there a multi-pin connector available that fits to the tow bar wiring plug behind RH rear light cluster, or do I have to cobble something up ?
The o/s is a 7 wire - the n/s a 4 wire - what is the function the n/s 4 wire connector ?
Finally, do I need a trailer indicator relay or is it built in to the car ?
Just fitted a tow bar and the boys in blue round here are getting keen on trailer inspections

They are TE Connectivity connectors, RS part number 531-4540 (https://uk.rs-online.com/web/p/wire-housings-plugs/5314540/) or 531-4607 for the 4 way. I can't remember which one fits into the plug that is there (one is for the plug, the other for the socket and the pics on the RS site should tell you). So for the other one (8 way but with only 7 ways used) you would need 362-9064 or 362-9187. You'll also need the connectors to go into the housings but they only come in packs of 50, part numbers 712-1911 or 712-1921.

The one on the RH side gives you the standard 7 wires for a 7 way trailer socket, whereas the 4 way one on the LH side gives the additional ones used if you have dual sockets or the modern 12 way socket. That one has a permanent live, ignition switched live, reversing light feed and ground.

Iirc You guys in UK and US have different plugs, but for the continental European market are ready made plug & play wirings available ... e.g. island4x4. Just installed one a few weeks ago for a friend ...
https://www.island-4x4.co.uk/towing-socket-harness-prc9232-p-19741.html

I think that's the new standard Euro 13 pin (where only 12 are used, hence 12N), original UK socket was a 7 pin which I assume is the same as in Europe (as I once bought a trailer in France and the plug fitted my car and all the lights worked). The US use a really weird 4 pin thing that isn't compatible with anything else due to them using the same bulb for stop lights and indicators.

Your BeCM knows when a trailer is plugged in. I get a green trailer icon light on my instrument panel. You don’t need another relay (mine is a NAS GEMS and I use a 4 pin NAS connector, so yours might be different).

Same with UK unless the trailer has LED bulbs without resistors fitted as they don't draw enough current for it to know you have a trailer plugged in.

Makes sense

I guess the genuine 7pin Plug / wiring kit part number is PRC9232?
A friend of mine has one for sale … still sealed / unused.

For us un civilized flat 4 pin Neanderthals here in NA, we have this:
https://www.amazon.com/Rover-YWJ500130-Trailer-Wiring-Range/dp/B0096W5F2G?ref_=ast_sto_dp

It is spendy, but is a plug and play option that works well.

Bolt … hold my beer 😉 You might claim Neanthertalism culturally for You, which I can only accept, but I have the geographical (birth)place Neanderthal within half an hour drive 😜

Let’s talk about heritage, tribalism and taste … #scnr

I somewhat like the American pragmatic effective way of trailer lightning ;-)
until we had multicolored LED we were thinking in individual complex signal light compartments and colors …
question of taste, of course …

Thanks to all - I managed to get a complete unit on eBay for £20 -