Body Slam for the Commodore 64 was a conversion of a 1986 Sega coin-op featuring female wrestling. The game was written by Jonathan French, Wayne Blake and Tim Follin at Software Creations.
The credits state copyright Firebird 1988, but Body Slam was most likely to have been earmarked for a budget release on the new Silverbird label in the same way that the Atari coin-op conversion of 'Peter Packrat' was (also written by Software Creations).
One possible reason for why Body Slam wasn't released might have been because the game slipped out via the Commodore 64 pirate channels in late August 1988. This was 6 months before TelecomSoft was put up for sale by British Telecom.