These people Patria Fidelis are based in Ealing the highest concentration of Poles in the country - some from right-wing areas in Poland, hence a base.
Occasionally they do stuff like "anti-abortion" firewall protests outside reproductive service centres offering services to Polish women. Britain is (after Germany, I believe) the number two choice for Polish women with money, an abortion is
very difficult in Poland, much harder even than Ireland or Portugal. Anti-abortionism is even a vote-winning approach in government there.
Notice the map eats into parts of Belarus, a marker of their revanchism. The Powstanie Wielko-polskie is the heavily mythologised Greater Poland Uprising - in fact a bitter nationalist movement of (anti-Bolshevik) army figures against Germans in the West and Belarusians in the East to re-establish a stronger, larger (landlord-heavy, drive out the Germans to give new land for the Polish poor) Poland during the Versailles Treaty period.
Sadly, because the government no longer funds any kind of second language education, (money for multicultural grants is often simply to patch up social services for the disabled or elderly) these people also do a lot of Polish language supplementary schools for young Polish children and have their own youth theatre groups - themes of their productions the usual folkloric stories and history plays about Roman Dmowski, Marshal Pilsudski, the Home Army during WW2 and the CIA-backed insurgents of the 1940s and 50s against the PUWP, which is what the protest in OP is about.
As J Ed points out their kinds of ideas - such as demanding trial, imprisonment and for SLD or even PSP politicians supposedly tainted by association with Communism (often ordinary functionaries teachers or civil servants) - match perfectly with those of the actual far-right back in Poland. Of course they claim they are non-political in a sense yes no party - just Catholic, Polish and traditional.
by which I mean their choice of banners/symbols
