Thanks for the replies people. As it turns out it was a lot cheaper than I expected. It was 9.40 euros each for myself and the girlfirend for a return from Blanes to Barcelona Sants. I for some reason was expecting at least twice as much for a journey thatt was over an hour and a half. (Just shows how conditioned we have become to high dares in this country). Journey was intresting as the line runs right by the beaches for about an hour. Including the nudist beaches which was an eye opener
Also intresting to note that when I purchased the ticket the machine was in Catalonian rather than Spanish. The ticket was also to a zone rather than a station which meant we caught the train back from Barcelona Catalunya rather than having to walk back to Sants. Catalunya is an odd station mind, reminded me of my local station (Sunderland) with a metro station sort of enclosing it.
As a side note, Barcelona is a fantastic city. We both hope to re visit next year when were on honeymoon