Landrover tow bar and electrics

Today i was in land rover and the sales man seemed to know about tow bars but then told me that even if you get a 3rd party to fit a tow bar for cheaper you still have to buy the land rover electrics or it will not work correct and it effects the cars ECU and electronic system on the car......So land rover quote around £900 to fit from them has anyone had a 3rd party fit it and does the car work correct? its a 2011-2013 Disco 4 or Rangrover sport.

Audi quoted me £1200 to fit and i got it done for £550 and works fine?????

Just looking for some info incase i buy a new car and end up in the Sh8t.. 

Thanks Craig