In reply to galpinos:
We've used a couple of cheap ones. The first was a Halfords one from a few years ago. It did tilt, but was very heavy and the clips that held the wheels in place were unreliable, overall a bit rubbish.
We currently have an old one from Pendle like this https://singletrackworld.com/classifieds/advert/pendle-4-bike-wheel-support...
Although it looks rubbish, it actually works well, and they seem easy to pick up cheaply. Disadvantage of it is that it doesn't tilt.
As others have said, be aware of nose weight. With 2 reasonably lightweight adult bikes and 2 kids Islabikes on it we have to be careful over speed bumps, and only just made it up the ramp onto the ferry when we went to Europe last summer.