I wouldnt get too hung up about the loco allocations - its enough to know the locos were shedded in the area at the time modelled - Most of my motive power is Newton Heath allocated (26A) because thats the shed whic provided the majority of locos - but not all, Ive a few Agecroft, Bury, Lees and Patricroft allocated locos which I knew ran on the loop - At its most extreme examples, the unamed Patriot 45177 was a very regular wakes specials performer, and that was Bank Hall (Liverpool) allocated loco, and Iron Duke was only actually allocated for 6 months to 26A over the Summer of 61, but it did run the loop!