Thank you for your reply.Yes the 18x eeprom can be accessed using read and write commands and, yes, it will retain the data during a power cycle. However, when you download software to the picaxe, it clears the eeprom.
If you want to maintain the eeprom values during a software update I think you have to have a routine to upload the eeprom values so that you can restore them after (or during) the next software download.