From the Official barcelona website:

http://www.fcbarcelona.com/eng/noticias/noticias/n04091410.shtml

Now you can purchase tickets for this season's first team football matches in the Nou Camp in this section.

Tickets for FC Barcelona home matches in La Liga, the Kings Cup and the Champions League can be purchased at the following sales points:

Spanish League

- FC Barcelona ticket offices
From Monday to Thursday, 9 am to 1.30 pm and 3 pm to 6 pm
Friday, 9 am to 2.30 pm Saturday, 9 am to 1.30 pm (weekend matches in the Nou Camp)
- ServiCaixa ATMs
- Telephone 902 18 99 00
- Internet. Buy here now

For the Racing Santander game I think you will be able to buy them when you get to Barcelona in advance of the game.

A source that says authorised agent but I am not sure.

http://www.barcelona-football-tickets.com/

Kind Regards
Stewart

thanks for the help, i had misread the website, to get tickets for european games it says you have to be a member and i'd assumed that was the same for La liga. I emailed barca and now have all the details i need, (i'd thought their email filter had caught my 1st queiry as they took a while to reply) thanks for the help. Pete.