Coming from London is a great icebreaker.
Pretty much every time you meet someone at an Erasmus event (or even generally out and about - the guy serving me at one of my favourite bakeries asked where I was from last weekend) the conversation will include 'Woher kommst du?', or 'Where are you from?'
Like most people, I have various answers for that, depending on where I was born, where I grew up, where I'm at uni, etc - but I tend to go for the one that most people will have heard of:
(The reason I don't give the country is that it invariably ends up with having to explain why Great Britain is different from the United Kingdom, and although I've got great at giving that explanation in German, Vereinigtes Königreich is a bit of a mouthful!)
The reason it's a great ice-breaker is because everyone has heard of London and knows where it is, and it leads into so many possible conversations.
'You sound like you're from LAAANDAAN' (most people seem to know that quote even if, like me, they've never seen the film... and yes, I've become excellent at imitating that line)
It often degenerates into talking about how my Mum can't always understand what my Scottish cousins say, or telling the story of the time I was in Washington DC and the guy on the other side of the McDonald's counter didn't understand my asking for a bottle of water (I gave up and had a Coke). It's a lot of fun, honest!
It also often leads into discussing how expensive London is, or other impressions of it people who've visited (or always wanted to) have had, which is always interesting, to see what people who've visited have thought of my home city.
Sometimes, with politics students, we end up having an in-depth discussion about the Scottish independence referendum, nationalism, and, yes, the difference between Great Britain and the UK. Hey, it takes all sorts! (Says the politics student...)