Spent ages trying to get through the moths-and-triffids area, and found it pretty hard going. Retreated instead, and worked my way around areas of the castle trying to find new areas (which I didn’t really manage), and secret rooms leading to power-ups (of which I found loads). My heart, HP and MP maximum levels were then somewhat higher than previously, allowing me to get through the moths to another save point.
I then wandered around to bump my level up a bit, and then found the next boss – a pair of dragon things. Which I can’t seem to kill. I mean, I can hit them – it’s just they seem to take a billion hits and there’s no great place to stand to whip them without being hit yourself.