Thanks for the report! From memory, there's nothing on the ground for pedestrians, bikes or scooters, but there is bike parking. So:

motor_vehicle=no
(Cars and motorbikes use the private motor vehicle side of the P&R)

bus=designated
(This side of the P&R is for the buses)

minibus=yes
(The little ST1 stops here, but these are *(big)bus* links. I don't think there's a distinction in UK law, however)

Not psv=<something-permissive> because taxis will use the private motor vehicle side of the P&R too.

Saying nothing about bicycle and scooter use without further ground evidence.