I assume you mean WWII? I don't see why not, though don't expect your character to be able to go running back to the UK immediately when shit goes down. :)
Yeap WW2, as for heading back home immediately after the event , whilst he'll express that desire reality for him will be ....theres no contact with family back home and so the family he has locally is .for want of a better term..'it'.
On top of that he's a kid in a foreign land, regardless of any external controls over travel ,he doesn't have the means, financially or otherwise to actually get back home...