I'm pretty sure you can dress as a Nazi or wave any form of their materials around, freely in the UK. Again, how you will be perceived by others is another matter, but it doesn't change your rights as a citizen of a democracy.

As rsh said, that is what makes us different, vulnerable or open to abuse some might say, but at the same time, the same freedom which allows it, allows you to express your own opinions about these factions.

Strange world.