I think there are two separate issues here:
The first is the threat to Jewish people in the UK - and there is no doubt that any current threat is from Muslim extremists, and maybe the odd EDL/skinhead idiot. Theresa May has no option but to order extra resources to protect potential Jewish targets.
Of course we are all at risk, but some more than others right now.
Second, is the recent survey showing an undercurrent of anti-semitism amongst the British in general.
People are outraged at the actions of Islamists, levels of immigration, Halal meat, etc., but I think we can't deny that there's a low-level visceral dislike of Jews, simply for being Jews.