I mainly see a mix of clueless westerners getting excited and joining in a bit of catchy chanting without thinking too deeply about what they're saying or impressionable youngsters with more passion than perspective being stirred into emotional fervour.
There are also a few opportunists looking for support for their particular brand of hatred.
So what it achieves is, some Jewish people feel intimidated, some British people will resent what they see and a bunch of protesters will feel validated.
Doesn't influence the government, doesn't help anyone in Israel or Gaza or the people there trying to broker peace and bring terrified captives back to their families.