BRE
www.bre.co.uk may be worth trying - they produced a video of their investigation into the fire, but it may not be available now. If it isn't obviously on the website, try contacting them.
The results of this work was reported in Fire Safety Journal, 3 (1980/81) pages 55-65, (Elsevier Sequoia SA) as "The Manchester Woolworth's Store Fire, May 1979: Burning characteristics of the Furniture.
Authors are W D Woolley, S A Ames and P G Smith. The article has a short summary of the fire incident as a lead-in to the test work.
Other BRE work following on from this was in two stages. Stage 1 was a look at the effect of sprinklers on the Woolworth's fire load and was reported to the Joint Fire Prevention Committee of the Central Fire Brigades Advisory Council (CFBAC) in 1982 - I do not know if any of this was published publically.
Stage 2 was an extension into sprinklers for life safety for the then Home Office, and a summary report "Sprinklers for Life Safety in Department Stores" on behalf of the Joint Committee on Fire Research of the CFBAC was published in 1992. (J A Harwood and B T Hume, Research Report Number 51.)
Besides the official report, 'Fire' produced reports on the fire in October 1979 and on the resultant inquest in July 1980.
