There will be a OneWorld transfer agent meeting the flight and holding a sign with the familiar purple OneWorld globe. They will tell you the best way to get where you need to be.

Especially if there are a lot of connecting passengers (which there usually are), they will usually run a bus from the gate to the T1 connection area. If so, the agent will direct you.

Basically, it should only take about 30 minutes to transfer, and you will NOT have to pass through HM Customs.