Originally Posted by LeisureFirst

Welcome to Flyertalk, kate1937.

I can't answer your question about maps, but really you have little to worry about. Everything is well sign-posted, and there's no way you'll be permitted to do anything other than pass through immigration, baggage collection and security in the correct order.

Although there are two exits from the baggage hall (IIRC) they both converge to a single exit from Customs which is where your cousin should meet you. So there's not much scope for confusion about the meeting point. Of course in these situations it is wise to have a back-up plan in case you can't find your cousin - people do run into heavy traffic or have other problems getting to the airport sometimes, but that has little to do with having a map of the terminal. Ensuring that your cellphone will work in the UK is a good start.

Unfortunately BA does not personally escort its First Class pax through the terminal in the way that premium airlines do. You'll be following the same route as everyone else but if you don't have an EEA or Swiss passport, you'll have access to the Fast Track immigration line which should speed you through somewhat.