Looking at the National Express schedule for Heathrow to Norwich, it looks like the coach/bus stops up at Heathrow Terminal 5, then Terminal 4, then Terminal 1,2,3, which I assume is a euphemism for the Central Bus Station.

So if my assumption is correct and if the OP is arriving at Terminals 4 or 5, no need for her to figure out the way to the Central Bus Station. She just needs to follow the signs to the bus stop area in her arrival terminal.