I can answer the phone plan question.
There are two options that come to mind:
- He can buy a local SIM. He’ll receive a UK number, which will be helpful to make local calls (and some schools/banks if he’s opening an account might even require this). The downside is that it’ll cost you to call him from the US, but you can use free calling with apps like WhatsApp. Phone and data plans are cheap outside the US.
- Your phone carrier likely has a plan that allows you to call any 1 country of your choice (outside NA) for free. Our carrier, Verizon, offers such a plan. The advantage is that he retains his US number so you and his friends here can call him for free and he can call back, plus he can call all UK numbers for free. But if he needs a UK number as mentioned above then this won’t help.
If he has a newer phone that supports dual SIMs he can do both of the above and have two numbers. This worked very well for my daughter (in another country, but it’ll be the same in the UK)
Edit: cross-posted with @SJ2727