[Tannaton]

You need to add a "trailer module" with the electrics and that needs a software update on the car to recognise it.

You can get generic lighting modules for some models but the Volvo system is by far the best as it alters the traction control settings etc. when towing. If you're just going to be towing a small trailer to the tip then a generic kit should be okay but if you are towing big heavy stuff or caravans, you are much better off with the proper Volvo set up.

Some dealers sell the new Volvo wiring kits on ebay, there's no reason why you couldn't fit a second hand towbar and a new kit yourself and then get your dealer to program it.