Just managed to watch it before it ran out on Iplayer, Alan.
I think we mustn't forget that the driver for all of this will be where the cargo owners want their boxes to go. Ultimately, they tell the ocean carriers which port they want the boxes collected from and landed at, and the carriers ultimately refuse at their peril, in the end. Both Felixstowe and Gateway ran major campaigns in China last autumn, selling their ports to Chinese cargo owners. Per box ocean carriage costs are more or less the same for any northern European port - Felixstowe, Gateway, Rotterdam, Bremerhaven - there isn't much difference.
An extra 4 or 6 hours steaming time, on a 40+ day rotation to the Far East, is also pretty immaterial for the lines - 19 knot or whatever speed slow steaming is nominal anyway, because ships have to vary their speed to meet their slots. The maybe extra 20 or 30 tons of fuel is neither here nor there - and if Gateway performs on its key promises of faster turnaround with less delays, the cost of additional steaming will be offset by being able to steam the next leg on the voyage slower.