Last train to London out of Birmingham New Street on a Sunday night is 11pm sharp. Gig will finish around 10.55 pm I reckon. You can get from the venue to the station in 5 mins if you leg it. Yer best bet is missing the final song of the encore I'm afraid :\ohwell:
Was in Brum yesterday and walked past the venue. The Scruffy Myrphy's bar is literally 1 minute's walk away. Think The End bar next door to the venue may be open also. Scruffy Murphy's was actually closed Sunday arvo tho the opening times stated open noon til 11pm