[theintern]

Definitely get a cheap sim card wherever he lands. The EU abolished all roaming charges for data and calls so he'll be able to use whatever data and calls he has in all EU countries.

Some countries have extremely good value pre paid sim cards with 20 gigs of data often coming in under €20 a month.

[pbalau]

No roaming charges between members of EU. So, if he lands first in UK, don't buy the sim from there