I am travelling to UK on a business trip. My company has provided me a visa letter with dates limited to the conference. I was hoping to stay for 4 days extra so I could tour the place and visit friends. How can I do this? Would the business visa suffice?
Just say so.
Include your itinerary, such as extra hotels/etc. Optionally in addition to company letter add a letter from yourself saying something like "I wish to stay a few days after the conference and visit local sights/another city/etc".