when I raced, some districts didn't use the distance suffix(?).
K courses (midland) and J courses (N.Staffs/Manchester) for example just used a number and sometimes a letter to identify the start point
K6 for example was based on the A449/A5 and started nr Cannock, K6s same roads but started at Dunston nr Stafford
I remember the K49 and the J57 were basically the same course in opposite directions. The K49 started in Rugeley and went to Stone and back on the A51. The J equivalent started nr Stone and went to Rugeley and back, the A51 being the boundary between 2 districts.