It's beginning to look as though no individual company was at fault here.
The manufacturer of the aluminium panels, Arconix, makes different types of panels. Reynobond PE, which was used in the cladding for Grenfell tower, is less fire resistant than Reynobond FR and the sales literature for PE says that it should not be used for buildings higher than 10 meters.
The panels were sold to Omnis Exteriors who acted as the fabricator, adding insulation bought from Celotex to the panels, which were then installed by a third company which had won the contract from the main contractors for the refurbishment of the tower. A statement on the Omins Exteriors website says that panels like Reynobond PE should only be used with a non-combustible insulation material if they are to be used on high rise buildings.
That information comes from a piece in the Guardian
https://www.theguardian.com/uk-news/2017/jun/26/grenfell-tower-cladding-linked-to-fire-pulled-from-sale-worldwide
That all sounds like some level of incompetence on the part of all parties concerned. However when driving home last night I'm pretty sure I heard on the news that the Minister for Communities and Local Government had said something about making a change to the building regulations. Can't find a link for that statement, but if true it would imply that in this country the building regulations do not bar the use of Reynobond PE on high rise buildings.
It is possible that, as long as everything used complied with the building regulations in force at the time, no individual or company involved in this disaster is directly to blame and that in the end all the talk of prosecutions for manslaughter will come to nothing.