My beans are bought from an independent local roaster (its actually only a few miles from my house and I go to pick them up so they dont have to ship them) Yes I agree they are just more oily than a light or medium roast and someone told me that the oils can cause issues sometimes, but that may not be the case I suppose.
I am really happy with my KinGrinder k6 for hand grinding and isnt a chore for one or two coffees, but anymore and it may well be.
I think I will look more at the conical than the flat but good to know that the flat wont be affected by the darker beans if the other features are better on a flat burr.
The Femobook might be a bit too much for me to spend, but will see.
One more quick option I have been considering is if there are any grinders in the price range with with grind to time or grind to weight options. Again this will simplify the process for others making espresso in the house.