Re the relief issue, if it's a nylon-strung guitar then relief isn't really an issue. As I guess you know, classicals don't have relief or bridge compensation - they work on the theory that nylon strings are light and don't change their pitch much when moved a comparatively long way. So they just raise the action at the bridge to allow the strings to clear the frets, and the extra height on the action doesn't bugger the pitch or your fingers too much with the nylon strings. But the symptoms of lack of relief and too low an action will be string buzz rather than tuning problems, so it doesn't sound like this is a problem on Rumncoke's guitar.