I think part of the problem is that there are so many recipes for "anglo-saxon oatcakes" on the internet that are all copies of each other and aren't at all authentic! Almost all are sweet cookie types for kids to make as a part of history lessons, and almost all use rolled oats, also not authentic.
Honey cakes most likely would have been a rare luxury for most anglo-saxons, only eaten on feast days. Coarsely milling whatever oats you have, whether labelled rolled oats or porridge oats should work to give the right effect.
The old lady's "cakes" King Alfred burned are far more likely to have been a type of unleavened flatbread, probably a mix of pea flour and rough milled oats or barley. This is an interesting article on what anglo-saxons might have really eaten and how they cooked them:
https://earlybread.wordpress.com/2017/05/13/how-to-make-everyday-anglo-saxon-bread-version-2-hearthcakes-or-kichells/
Reminds me of the excellent article you wrote on using wood ash for leavening!