I find it odd that there are people who love the taste but dislike the smell. I usually stop in my tracks when I catch the fragrance and will go up to the fruit to drink in the scent - delicious!
I've had mixed results eating it in London, the first time I tried it the texture and some of the taste reminded me too much of a rotting onion, and not a particularly sweet one. Next attempt was much better, the fruit tasted much more closely to the smell - buttery/vanilla/citrus is a good description I share with the poster above.
However, perfectly ripe mangosteens remain my favourite fruit and these are even more elusive for a London dweller than decent durian.