Fitted a swivel for the front seat today. Easy ten minute job, and the thing does what it’s supposed to do, it swivels the seat to face backwards.
To fit it, the seat was removed from the base by undoing the four Allen bolts that hold the seat rails to the base.
The swivel plate then bolts to the base using the four countersunk bolts supplied with the seat, leave them all loose until you’ve got them started into the threaded holes in the base. Then tighten them up.
The orange handle on the swivel needs to be facing the handbrake, pointing upwards.

Then drop the seat onto the swivel plate and use the Allen bolts you removed previously and four 13mm nuts to bolt the rails to the swivel, again fit loosely until all are located.
When fitted the seat can be swiveled 180 degrees to face into the back of the van.

I like it when things do what they’re supposed to do without any fecking about.