ESP8266 C FLASH Saving of Variables

While I’m off in search of a C one-wire library, has anyone saved any variables to FLASH (hence non-volatile) – and if so would they care to give the simplest C code example of how to do that?  I (and no doubt others) would like to save some strings and integers permanently or semi-permanently – or even perhaps some log info – we have loads of Flash but personally I’ve not idea which bits I can safely use or how to do the read and write….  So kind of like the equivalent of Arduino EEPROM library.

Please note – this information has now been superseded by the info on the new blog at http://tech.scargill.net – please visit the new blog.