Owen, it strikes me that you have a bit of a naive perception of Victorian London, if I may say so. In the 19th century, as now, there were all kinds of troupes of all kinds of entertainers travelling the world, and the more exotic, the better, so to speak. Impresios scoured the world for the new and bizarre, to bring to public theatres as well as to the salons of the wealthy. As you say, we're talking about the Empire at its height; the stay-at-home portion of the British populace would naturally have a thirst to see in the flesh the strange creatures, persons, and practices of which they had heard so many travellers' tales.

Not to mention that in London there were already - at least such is my impression - communities of people from distant parts of the world. A person with the curiosity may well have had plenty of opportunity to hear 'ethnic' and 'exotic' music.