Way back BHM had an early Gdi which turned over but would not start. After all the checks, I believe that they cranked it for a long time, and it suddenly awoke. That's all I know.
It happened to mine, plus a couple of other GDi's I know. You're right Dave - Keith at BHM cranked it over for about 15 seconds and it fired up. It worked on the others too. I believe it was due to unspent fuel seeping down past the piston rings causing loss of compression. Cranking it over restored compression.