Trip to london, any ideas?

Me and my friend are going to london next summer.

Im english and live abroad and she is foreign but speaks good english.

We are probably gonna do all the normal turisty stuff (Oxford street, millenium eye, Buckingham palace,tower of London) but would also like to see some other lesser known cool and interesting places and things. And if they were free that would be even better but they dont have to be

Both of us are big doctor who, harry potter and Beatles fans.

Also if you know where a good place to find alan rickman, emma thopson, helena bonham carter, tim burton and J.K. rowling i bet we could entertain ourselvs

ooo, and david tennant and matt smith

Dont judge us :)

would love some ideas

:))