If it was me i would probably just pay the £30 extra to fly from Barcelona to save yourself the hassle as i guess if your going by public transport it wont be much less then that and then your last day of hols is spent messing about travelling, when you could be having a Sangria in Barcelona. They are not that close and there is not a lot going on in Reus, Tarragona is nice and worth a visit not far from Reus airport.