Most of these are too inarticulate to come up with something new - they just look for the lowest common denominator.
Is it historical ? Do they blame the Jew's for the invasion of Poland or something?.
Hatred of 'the other' by essentially rural semi-literate people along with distaste of traders and the "ger orff my laarnd" farmer v. nomad thing that's as old as Cain and Abel. Plus a deep-seated inferiority complex due to being invaded so often and a need to blame others and of course the fascho/hooligan thing is a ready made bit of camaraderie that appeals to uneducated but aggressive young males.
Do they blame the Jew's for
I've known certain Poles blame them for double parking, a loss at football and even the weather. These people are in a shrinking minority though.
A shame it's spread to London, however the demographic of poor, uneducated provincial people (remember the economic and educational elite don't have to go to England to work in Tesco's) who went means statistically there are bound to be a few. The ill-adaption of people like that just encourages sticking together and of course the UK skinheads and their foul 'music' bands have long been idolised by fascists across Europe.
Sad really, but all of them inadequates and not a threat to anyone.