Ooh, that's rather short notice. (The best advance deals are usually available about 6 weeks prior to travel). Travel on Fridays is also the hardest day to find any good reductions.
Your first way of doing it doesn't offer any good discounted fares unless you're prepared to travel back the long way round (Fareham > Basingstoke > Reading > Newport > Hereford) departing at 2124 and arriving back in Hereford at 0146. That part of your journey would then only cost you £14.00. You could combine that with outward travel for £19.00 (available on the 0945 service, changing at Newport, arriving at 1327) or £25.00 (available on the 1138 and 1238 service, changing at Newport, arriving at 1527 or 1627), giving a total return fare of either £33.00 or £39.00.
Using your second option, you've still got the £19 or £25 outbound services, as above. Regrettably, there are no discounted tickets available on the return service from Reading to Hereford on the Saturday morning. You'd have to pay £30 for an off-peak single. There are early morning services, via Newport, at 0554, 0654 and 0753 but it might be better to have a more leisurely breakfast and catch the 0854 train, as it runs direct to Hereford (arriving at 1142).
Chris