Price has dropped even lower (£2.14 each) for the HX8357B displays here. (Ignore the claim they are ILI9341!)
That fixed it. Now it looks great. Can't say I see any slowing of the operation. Still MUCH faster than a UNO, that good old workhorse board.
I have added support for 8 bit ILI9481 displays here (cut and paste link as forum does not support banggood links):