Several people have mentioned how extensive the fragrance section is at Fortnum and Mason. On Saturday I finally had the chance to visit, and they do stock a lot of niche lines. that are hard to come by elsewhere. It almost rivals the Liberty perfume room if you ask me.
Niche brands in Fortnum and Mason include Grossmith, Annick Goutal and Clive Christian. A large section of the third floor displays are room fragrances from lots of different companies. Definitely well worth a visit.
It's hard to find any information on the Fortnum's website about their perfume section.
And here's a glimpse of the Caron display:
Whilst in Mayfair, I quickly popped into Ormonde Jayne, where they were kind enough to give me a sample of Tiare. I'm toying with the idea of buying a full bottle. I'll see how I feel about it after I've finished this sample.