Nick, there is a clear pattern that people who do not live in the USA who are strong fans generally prefer TNG, while strong fans who live in the USA are more likely to prefer TOS. Now, I live in the US and prefer TNG, so I'm not suggesting this is a hard and fast rule... but there does seem to be a tendency. In spite of it's supposed international crew, TOS has had little appeal abroad. You can even see it in the JJA Trek numbers. Most comic book and space-based Hollywood productions nowadays get MOST of their revenues overseas, while JJA Trek did not.
I don't believe that's the case in the UK. My impression is that TOS is just as popular as TNG here, if not moreso.