gah havn't watched that in ages. from memory though:
edward tried 'belonging' with the family? but couldn't due to external barriers (physical features) similarly feliks tried to belong shown through his attempt to "keep pace with the Joneses" however was unable to due to a cultural barrier.
umm.. despite feeling a connection with the family (or little girl was it..i dunno) he did not fully belong which shows the need for acceptance. similarly, feliks was not accepted by society shown through the dialogue/rhetorical question "did your father ever attempt to learn english?"
a sense of belonging is dynamic, and is constantly subject to change. while edward was initially alienated he eventually established a connection. similarly, the persona's sense of belonging with his polish culture diminishes as he "[forgets his] first polish word" and begins "pitching [his] tents further and further south of hadrian's wall".
and that's all i can come up with, goodluck!