To correct a few points : Guernsey is class D airspace at this altitude, so you need a transponder to enter, they normally do not give exceptions .. Any aircraft whatever its registration nationality that wants to fly in EASA airspace requires a mode S transponder . Mode A/C are no longer to be used,, In the USA you can still use the old A/C transponder but then you cannot enter, let alone be based in European airspace.
Same for ELTs, to fly in a powered aircraft in the EASA airspace you need a 406 ELT. As correctly said they normally activate on impact . but if antennae is damaged on impact or under water it does not work ( i.e AF447 , MH 270, etc.. )
To cross a EU border you need a flight plan , and yes there was an IFR one filed . not night VFR
Sadly this morning on French radio played a recording of Sala from inside the aircraft ( in Spanish) said to be afraid of the poor state of the aircraft .:-(