How do i get a cheaper rail fare?
For a single fare on that journey £19.80’s not bad – you’re travelling in the peak hours (before 0930) on a weekday, and the National Rail timetables/fares site shows an anytime single fare at that time is £30 adult, and a return the same day at £47. I’m surprised you can get that much of a reduction as there are normally minimum fares with the young persons’ railcard before 1000 on Mondays to Fridays (except Bank Holidays, and in July and August). If you were travelling after 9 a.m. the same day, you could get a single for £22.30, less railcard discount. I don’t know why there don’t seem to be any “advance” tickets available, but I doubt they’d be available in peak time anyway.