Honestly, while there are places there that Who has used, most notably Trafalger Square (which is a must see), I would suggest you go and just enjoy all that London has to offer. It's a great city, the Underground is super easy to use and beats the street traffic and you won't be bored.
I was there in 2002 for the first time and we went everywhere we could and never found ourselves lost for ideas. But, if you are set on Who locations, I know there are websites out there that list them, though I don't recall which sites.