Thank you to everyone for your help.
It does seem right now that I have no easy way around the problem so i'll live with the Ember Bold font Amazon have supplied. I have around a thousand personal documents in the Amazon Cloud and that's far too many to delete and start again, even if I had a workaround.
Generally its a historic issue anyway as I used to buy from Independent Publishers but now i only buy from Amazon as most of the Independents have closed.