As it has allready been mentioned +
Budd - perhaps some Black Tie accesoires?
Savile Row no 1 - Gieves & Hawkes, marvelous building, used to be The Royal Geografical Society - this is where David Livingstone planned his African travels! - have your shoes shined by "The Shoe Snob".
Turnbull & Asser - bespoke department, entry from Bury St., ask to see their scrapbook, you wont believe what you see!
John Lobb, St. James's - ask if you can see the downstairs in particular...