Thanks for the reply.
Just wish Amazon would be clearer on how things work within the DP.
I tried to change the price of the ebook again but to no avail, so ended up updating the ebook with a new file. This has allowed me to change the price but of course I now have to wait the 24 hours or so for it to be published again.
As this is all just an experiment at present, I'm happy to just go with the 35% royalties.