The problem arises because every different music paper had its own chart at the time, some of which were more than a little suspect because of the small number of retailers they sampled. The NME and Melody Maker were the two most widely read papers, and they did both have it at No 1.
However, the industry's view was that Record Retailer, which they regarded as the trade paper, was the most accurate. This was because it had the widest sample of retailers reporting sales.
Tim Rice's Guinness Book of Hit Singles has it as only reaching No 2, as does its more recent Virgin successor.