We're very fortunate to have 3 good, specialist tobacconists here in Edinburgh (I believe there's only one in London).
There's The Cigar Box on the Royal Mile (just across from St Giles). Mainly cigars (the clue is in the name) but there is a decent selection of tinned and loose tobacco. Full range of Samuel Gawith and Dunhill blends, along with Ashton and Davidoff.
We've also got Robert Graham on Rose Street (between Castle Street and Charlotte Square). Nice selection of pipes and some excellent tobacco.
There's also The Pipe Shop on Leith Walk (near the bottom on the left hand side as you head down). Friendly, helpful staff and a massive selection of bulk and tinned tobaccos. They've got a lovely selection of pipes on display, both briar and meeschaum.