I've always given things from the food section of Harrods (Tea/shortbread as above said) from the UK, or Peninsula (Tea/chocolates) from HK as omiyage (souvenirs from "where you travelled from") if I'm staying at someone's place (*ryokan/minshuku/friend's home) as suggested above. Single Malt is also a good idea for hosts who drink (if I'm not sure, I would go back to the earlier suggestion)
As a benchmark, I'm thinking Fortnum and Mason isn't exactly the best option unless you have your very last budgeting issue... given that the difference in price of tea COULD be v small between the 2 places. I don't intend seek attention by naming brands, but I think Harrods is a brand that is more respectable in Japan (or the Pen, in case from HK).
*one place my parents (usually) or my gf+me visit at least once every year around foilage. I always bring some something special, I believe my parents do the same. But I don't do it to other one-time places.
Originally Posted by
nancypants
disclaimer- my locales were Sendai and northern Hokkaido so people may have been slightly more parochial and easy to impress. This was also in 2006 and I gather there has been something of an explosion in tourism since then
I dont think most Japanese would mind too much - unless you run into a connoisseur of some sort, some product of the top department store would be respectable enough.