A quick entry until we get more details, but an article at http://www.hardcoregaming101.net/wheretimestoodstill/wheretimestoodstill.htm suggests that a C64 conversion of Wreckers was in production, but only 16-bit editions were released.
However, there was no news of any C64 conversion, and it seems that the game was only intended for the ZX Spectrum from Denton Designs. The game was 128k, and likely would have hit the same issues as Where Time Stood Still, hence why an attempt may not have been made.
Prepared to be surprised, but we suspect it will be a case closed before we know it! :)
Contributions: Fabrizio Bartoloni