Ah well. A quick Amazon order later and a micro SD card and an adapter was on the way. Those arrived here this morning, so I quickly prepared the micro SD card.
I had a bit of fun getting decent video on my rather old monitor in the shack and was starting to think I wasn't going to find something better than VGA! However, a setting of hdmi_group=2 and hdmi_mode=16 gave me a reasonable compromise between getting a decent amount on the screen and being able to read it without green and yellow flashing in the background.!
Then I installed RTLSDR and tested it, without any problems. I installed DUMP1090 - the ADS-B decoder as well as the Piaware software which uploads the ADS-B spots to Flightaware. Those programs run quite happily at the same time as Gpredict and use around 7% of CPU.
I fired up the Epiphany web browser and went to Twitter - again, the CPU was quite happy.
This looks very useful. I think I'd better order it a case!