AIP entry for base states 'ATIS service is subject to downgrade to A/G at short notice'. With Aerodrome Operator duties of care applicable in either case there is not much difference between the services. Traffic information is passed both under FIS and A/G in the interest of Rule 45 compliance to enable flight to be conducted safely within the zone, and a close eye is kept by the Aerodrome Operator on runway occupancy in the interest of customer service obligations, so there ain't much difference...apart from staff costs. Aerodrome Operators wouldn't like it if CAA SRG insisted upon a consistent type of service for no apparent reason. At base only a very small number of movements actually legally require FIS so the service is, most of the time, already over and above what is legally required. It would seem that remuneration for FISOs in the London area is generally about one and a half times the National Minimum Wage.