The Cupperty Ceremony
Every bit of food and drink in both seasons has a metaphorical significance, even if you don't realize it.
Tea is no exception. Its one of the few times an eastern philosophy creeps into Good Omens, but it still meets with a western ideal. It's also intrinsically linked to Aziraphale and his affected British style.
Coffee gets more of a focus in S2, and has a specific meaning around freedom and liberty, whereas tea appears more in S1. But the metaphorical meanings around them are fairly consistent across both seasons, with stereotypes for the British drinking tea and the Americans only drinking coffee put aside.
Lets start with Muriel on the doorstep of the bookshop, at the beginning of S2E3, asking to come in, because its noisy outside.