Some guidance here to help you, just follow the yellow signs and the general flow of people.
http://www.heathrowairport.com/heath...ing-passengers
http://www.heathrowairport.com/heath...-and-passports
http://www.heathrowairport.com/heath...ers/uk-customs
The immigration will be fairly straightforward and they will may or may not ask you some questions. You are a non-EEA national.
The customs channel you go through is nothing to declare, don't go through the blue EU arrivals channel.
Remember that many food items are banned from being brought in from outside the EU such as meats or plants, however this rarely enforced.
