Hi Vivien,
Thanks for your message. The most authoritative source with regards to hand and hold luggage is the CAA: https://www.caa.co.uk/passengers-and-public/passenger-guidance/baggage/safety-advice-on-what-to-pack/
Adaptors are fine in your hand or hold luggage.
If you have a traditional phone plug and cable for your phone, this are also fine to place in your hand or hold luggage. However if you have a portable power bank to charge your phone, this must be packed in your hand luggage and security may ask you to take this out of your bag to present for checking.
I hope this helps and have a great holiday!
Just You