Does a sub-250g FPV drone require the operator to be registered with the CAA DMARES (Drone and Model Aircraft Registration and Education System)?
No. If the FPV camera provides a live feed only, for the purposes of flying the aircraft and for avoiding obstacles, etc, then the operator is not required to register with the CAA.
Also, if the RC aircraft falls under the definition of a toy the operator does not need to be registered.
1.3 (page 31) says: The provision of images or other data solely for the use of controlling or monitoring the aircraft is not considered to be applicable to the meaning of ‘a sensor able to capture personal data’ in relation to the registration of UAS operators within Article 14 (5)(a) ii of the IR.
“This is ultimately a decision for the operator to make; if the FPV camera is not a ‘sensor able to capture personal data’ then the operator is not required to register him/ herself.”