When buying train tix I always go direct to the company providing the service as they will ALWAYS give you the cheapest price - Lancs to Manchester Piccadilly for e.g. is run by First TransPennine Express and a last-min open return ticket would cost you around £17, or £11 with a 16-25 railcard (STRONGLY recommend you get one, will save you 1/3 on all train tickets and only costs £30 a year - £27 if you use their 10% online discount). However in terms of coming home from gigs the last train departs from Manc around quarter past 10 which is a bit awkward, unless you wanna wait 'til 5am for the morning services to start!