Thanks for the info, Crossforth. 319424 could only have been on the 1131 ex-Wigan, due Lime Street 1222, actual arrival (according to RTT) 1222 and a quarter, with your own train departing at 1221 and three-quarters.
Tracing the duty through gives an Allerton finish, and that is consistent with DJH1971's sighting of it this morning. Assuming no interruptions, its duty today is one of the most straightforward of all those of the 319s, it simply departs Lime Street every two hours until 1900, and Wigan every two hours until 2003, although on its last trip it should collect a second unit (off the 1832 ex-Lime Street) at Wigan.
So it looks as though I'll need to wait at least another day before I see it in Manchester.
Is it in full livery, with bubbles and blue ends?