Small Unmanned Aircraft (SUA) flown under FPV are defined under a separate exemption from Small Unmanned Surveillance Aircraft (SUSA), although the rules broadl

Small Unmanned Aircraft (SUA) flown under FPV are defined under a separate exemption from Small Unmanned Surveillance Aircraft (SUSA), although the rules broadly overlap. Additionally for FPV the CAA mandate you must have a competent observer who can maintain unaided visual line of sight with the aircraft at all times. I suspect their 150m surveillance rule is part privacy, and part a belief that if you're trying to film something/somebody with a camera you pose a higher risk than if you're just flying past them.