Upvote:4
Your Schengen visa isn't valid for the UK although it might make it more likely that you'll be granted a UK visa.
You can check the UK government web site to determine what visa you might require, if any.
In your case, as a Pakistani citizen you will probably need a Standard Visitor Visa: the web site I linked to will tell exactly what you need if your needs differ.
You can apply for a visa through TLSContact, who have centres in Munich, Dusseldorf and Berlin.