The school used near the beginning where Marcella's daughter has been caught taking drugs is Charterhouse where Ralph Vaughan-Williams, Jonathan King and the founding members of Genesis were all pupils. It's signposted just off the A3 after Guilford.
The 331 bus runs from Ruislip Station to Belmont Road. The journey should take 53 minutes. Hampstead Heath is around a 5 minute bus journey from Belmont Road.
The incident involving Cara and a car is repeated in The Bay s2e3.