Clyde1998 With the station at Green Park now being open, the number of people using the buses (especially to the town centre) would probably fall anyway.
F1 bus return is now £5.50. Off-peak day return from Reading Main to Reading Green Park is £3.10.
14:37 gets you to Green Park for 14:44. It's 14 minutes walk to the Megastore from the station. Or you can play it safe and get the 14:07.
There's a train at 17:14, which depending on stoppage time, might be doable, and you're back in Reading before half-five.