@Eutychus,
back to your account of 2 flights in small piston engine to and from Jersey : you can only consider that you are transported by professional people if the aircraft operator holds an AOC.
The list of AOC holders in Jersey and Guernsey is here (page 32) :
https://cidca.aero/CHttpHandler.ashx?id=115363&p=0
Under some conditions, air taxi UK AOC holders can also operate from the Channel Islands. The list is here:
https://www.caa.co.uk/Commercial-ind...-Certificates/
Until recently (and but for a handful exceptions), air transport in IMC could only be performed with twin engine aircrafts.
See, for instance, the Beechcraft BE-90 for low profile operation,
Since 1 March 2017, EASA has issued a regulation that authorises IMC operation with single engine turbine aircraft (example: Cessna Caravan, Socata TBM, Pilatus PC12).
So you could come across AOC holders operating single engine
turbine aircraft.