I went on a tour of Mildenhall with a relative stationed there. Had to have photo id and be signed in by a service person with ID.
It is more US than anything and the outlets deal in Dollars. IIRC one fast food outlet would accept £ but gave the change in $ & c.
The PX was something else and cheap items everywhere....... Ford Mustang or similar for $30, 000 anyone?
The relative told me that some of his comrades flew in to the base from the US and never went outside the perimeter the whole duration of the tour.