Got a three bike one from decathlon, think it was around 170 quid plus buying another number plate for the integrated light board, dropped on straight out of the box
There are two cast parts that go on the towbar ball first and then the carrier drops on that and two bars push down and lock to tighten everything up
Very simple on and off in minutes , because i drive a 4×4 roofmounts are a PITA due to tge height- this has been a revelation
Its made by mont blanc for decathlon
The only downside are the wheels straps that were too small for 2.4 tyres but sourced some more for a couple of quid
Heres a few pics so you get the idea- this is a 4 bike but just the same
http://www.towequipe.co.uk/products/allroad4-automaxi-allroad4—4-bike-towball-cycle-carrier.html