I agree too but here's a bit more detail...
Not just west of Oxford, EA "registration" rules apply on all their water i.e. from the PLA boundary just below Teddington, all the way up to Lechlade, plus the last little bit of the Kennet at Reading including Blakes Lock. You pay at the first EA lock you come to where someone's on duty.
I think any powered leisure boat counts as a launch, and charges vary according to whether you buy a "day", week, month or year. Within that you pay by area in square metres, defined as length x beam, and the charge gets bigger according to what bracket y