However, as far as I know, they did successfully use the Vixen to replace the Meteors so they must have been able to do it.
I have yet to find a reference which confirms unmanned operation of the Sea Vixen when converted to the D.3 Drone. Evidently they could be controlled from the ground but it would appear that a standby pilot was onboard (to operate the fuel system?).
Targeting at Llanbedr
Between 1977 and 1985 the aircraft was converted to a D.3 drone by Flight Refuelling Ltd and flew as a manned drone from Llanbedr from 1986 until its retirement in 1991.
Sea Vixen Drone (D3) Era - SeaVixen
3. Testing. All the test flights during the development took place with a pilot in place but he was able to fully mimic the intended remote control as a push-button matrix was installed at eye level. So all the commands available to the ground operator could be produced by the pilot, ie bank left, bank right, climb, descend, throttles open, undercarriage up / down etc. After the early flights the test pilot was able to completely fly the aircraft from take-off to touch-down using the push-buttons (around 20 if I recall correctly) with the new drone avionics turning the simple button pushes into control surface and throttle movements.