RBS appears to have fouled up the scheduling of their overnight batch run in a way that meant large tranches of transactions simply weren't going through the system. Fixing the problem has taken days (which may be down to poorly managed outsourcing) and it's then taking even more time to catch up with the backlog of unregistered transactions, because they can only fit so many extra into the overnight run.
If you've got a pay slip or something, then get yourself to an RBS branch and they'll give you cash to tide you over in the meantime. Don't starve yourself!