I bought mine some years ago from
roofbox.co.uk. I found their website to be well laid out, informative, easy to use and I bought a tow-ball-mounted, 3-bike, wheel-supported carrier for around £100 IIRC. It was for a LR Disco 1 and can drop down to allow access to the rear door - though, TBH, it's not much good, as the door opens sideways, not up.
The one I got was reduced and it weighs a ton - but it's a very strong, secure bit of kit and has a wee padlock to lock it to the ball. It doesn't fold for storage either, which is something you might wish to consider.
Takes me 5-10 mins to put from garage to ball and, if using the same bikes and I have the wheel carriers already set in their right places, about another 5-10 mins to mount the bikes. They are held by rigid wee 'poles' and a webbing clamp round the top tube and the wheels also have webbing straps holding them to the carriers. Very secure and no worries at all when driving (once I've overcome the initial fears and checked the straps after 10-20 mins driving

)