https://www.velocirax.com/

Does anyone sell anything like this in the UK?

That is virtually identical to a Northshore Shuttle rack. They mount via a “receiver hitch”, which in this case is a 2″ square section tube about 8″ long where your towball would be. Carrying over 100KG of bikes, plus the weight of the rack would be beyond the loading of most European towbars.

I have seen Thule 591s mounted vertically on the rear of Transits.

The closest UK equivalent is a Scorpion Rack – http://www.scorpionracks.com