Off-peak returns with railcard discounts = £20.55 (each), total £41.10.
Valid on the 0930 Arriva Train Wales service from Manchester to Carmarthen, change at Crewe (arr: 1005) for the 1022 London Midland service from Crewe to Birmingham New Street (arr at Birmingham 1118), change there for the 1130 Cross Country service from Birmingham New Street to Cardiff (arr: University at 1136).
Numerous return journey opportunities on the way back, most (if not all) requiring a change of trains at Birmingham New Street, and then direct to Manchester Piccadilly. If you left University (at Birmingham) on the London Midland service to Four Oaks at 1605, changing at Birmingham New Street at 1612, you could then get the 1631 Cross Country service to Manchester Piccadilly (arr: 1759).
N.B. With off-peak return tickets, they would still be valid for earlier or later departures on your way back, if you so wished.