Does anyone know if there are power sockets in PE?
Yes, two options....
If you fly on the newer metal (refurb lgw or new a333 there will be USB connections to simply plug in.. Note that you can not be seen to 'charge' but the power lets you use your device without loosing power.
On the a346 you will need an empower converter. I purchased one from eBay for £4 ... The socket is at the bottom of the tray store, underneath the arm rest. There is no power option in econ class on this metal.
Not 100% sure if A343 has the empower adaptor... I would assume yes as they have the most up to date PE seat, just has an ife system from the 1980s