I am sure dragartist is correct. I know of no clearance for the dropping of vehicles via ULLA. That the USAF were able to do so with their similar system, LAPES was because of the specialist nature of the vehicles used as I mentioned earlier. I only ever dropped combat stores. That is ammo, rations, pol and the like and the APFC. I remember being told that our vehicles would not withstand the forces involved.
As regards the HSP when Op Corporate was brewing up I was asked by someone 'futher up the line' what I could recall about the HSP which had to all intents and purposes been withdrawn from service. I told him what I could remember and heard nothing more. It seems the 'cunning plan' was to drop a grader on South Georgia to make a tac strip for the Herc! Anyone who has ever been there or read Ernest Shackleton's book will be astounded that this was ever considered.
It is a measure of the desperation that the whole 'mission impossible' Falklands op generated. It was not the only 'interesting' proposal to come down the line !