Peugeot 308 2.0 diesel issues

[Elroy Blue]

Relative has a 2015 308 2.0 diesel GT. It's suffering intermittent cutouts when it's doing around 60mph/3000rpm. If the engine is switched off it usually comes back on again.
The fuel pump (in the tank) and the fuel filter have been changed, but it's still doing it.
It had an code reader plugged in and there was a fault code for the fuel pump, but changing it hasn't fixed anything.
Not really got any other ideas and a Peugeot dealer it's likely to just change parts at random.

[littleredrooster]

Ignition switch, perhaps. Take all keys off the keyring to leave only the ignition key and see if it still does it. Mate of mine had exactly this, weight of the bunch of keys gradually wears the barrel to the point where it starts making poor contact with the switch.

[Elroy Blue]

Thing is it only does it when the engine is under load. For example accelerating on the m/way or dual carriageway (from 50 up to 70 for example). The guy who changed the fuel pump and filter suggested it's a fuel pressure problem, but changing those hasn't solved it