The resources provided here cover all lichens, not just those reported for Greece. They also include some information on lichenicolous fungi. Though far from complete, you may find them helpful.
They were compiled largely independently of the usual sources, such as Index Fungorum and Zahlbruckner's Catalogus, and in many places they differ from what you will find in those sources.
Here is a summary of lichen nomenclature (pdf) so far as I have been able to determine it. (Note added 29 Aug. 2017. Viewing with Firefox (which may hang or exhaust memory) or Opera (which may mangle the fonts) may fail. Internet Explorer and Chrome are OK. I haven't tested Edge or Safari. If you encounter such a problem, don't try to view the file within your browser. Instead, download it directly to your hard drive, and then view with Adobe Reader. For Opera, go to Settings / Websites / PDF Documents and check the box "Open PDF files in the default PDF viewer application". For Firefox, from the tools icon (top right) go to Options / Applications / Portable Document Format and set to anything except "Preview in Firefox". The file will then be downloaded directly to your default downloads directory. The pdf file itself appears to be OK. There are no problems reading it in Adobe Reader, and the bug is probably within the browsers themselves.)
If you work with old literature, you will often have to seek a basionym for a combination that is introduced cryptically. I have found this list of epithets (pdf) helpful for that purpose.