All updated, compiled and worked immediately - I shouldn't have worried!
Not much faster than using the shield config though, takes about a second to draw a bitmap over most of the screen (the screen is 400x320, my bitmaps are 400x240 due to the old, shield screens I was using). I guess it might be the speed I'm reading from the SD card, 20 pixels at a time. Might try upping that to see what happens. I'm using the BMP display from the examples, slightly modified to work with Mac BMPs which seem very slightly different to BMPs from, I assume, Windows? Anyway, the ones delivered in the example. Mine seem to use 32 bit pixels, not that an alpha channel has any purpose in a BMP.