Harrod's of London celebrates the best of British at The Tea Room, featuring a quintessentially English line-up of mouth-watering fare, crumpets included :) http://www.harrods.com/content/the-store/restaurants/the-tea-room/

If you have still not gone on your trip. Try Fortum & Mason or Liberty ?20 -40 should get you a good experience

You might want to check out Circus - http://circus-london.co.uk/entertainment.php There are a bunch of circus-type performers and they eat fire and such. Honestly I am not entirely keen on the food, but its OK and the entertainment kind of makes up for it.

Of course it depends on your interests, but the Camden area of London has some interesting personality and you can get Nitrogen Ice Cream at chinchin. Or if you are into art, there are quite a few smaller art galleries that are pretty unique - mostly on the East End, which has been a bit of an up and coming area for a while now.

I have always been one of those people to be oddly fascinated by the whole Jack the Ripper thing.. so i have always kind of wanted to take a tour of Whitechapel myslef.