It is important to note that even with scrabled headcodes the first number is always correct. For example 654T which could be 6V00, and 703X could be 7C06
By this you can tell what load it is without needing the real headcode
The rules are
0 - light loco, 1 - express passenger + 1Z99 recovery, 2 - Slow passenger caroline service, 3 - specially authiorised workings and departmentals, 4 - fast freight and intermodal, 5 - ecs, 6 - freights mainly aggregates and ballast, 7 - 45mph freights, 8 - even slower freights and some departmentals, 9 - STP workings and high speed services and some other special authorisations,