A northern based aircraft would work a lot better than a southern based one as people need to get into London earlier than 10.30, which it would always be as the fliht didn't land in STN until 09.10. I was on it myself a number of times and there was always people running to get the train/bus to Liverpool Street in the centre.
However, basing one aircraft in the North would not be economically viable for an airline like Ryanair.