For those interested, in addition to their 60-83-71 code, Starling also have:
04-00-10, 04-00-11, 04-00-23, 04-00-40, 04-00-42, 04-00-47, 04-00-48, 04-00-49, 04-00-50, 04-00-51, 04-00-54, 04-00-55 and 04-00-59.
Some of those are used for their BaaS customers, for example 04-00-48 is used for Raisin and 04-00-49 for Ditto Bank (France).
Monzo have 04-00-03 through to 04-00-08 by the looks of it.