Pieter, I print from LR to an Epson Stylus Pro 7900 (using a custom paper profile) - same set up for the last 4-5 years. Console has a vast amount of information but I can't see any note about cups today. I've emailed Adobe about the issue and will await any reply before trying the 10.9.5 updater.
Manoli, I just print from LR6, and also Epson Printer Utility 4 for nozzle checks. The c0000x files are of constant small size but the d0000x-001 files vary accoriding to print size, as mentioned, from between 218.1 MB to 1.8 GB. Definitely imaging print files as you can see them popping up in Finder as soon as the LR printing is initiated. I changed permissions of all the files yesterday but it didn't make any difference. Could you detail precisely the further permission checks you had in mind?
Thanks very much again to you both for your further suggestions.
Meanwhile, it's no big deal to manually delete these files while awaiting a definitive understanding and solution to this issue.