Im coming to salou in july but my passport expires in september,does anyone know if i need to renew it now...or will it be ok. Thanks

Depends upon how long you are going to stay! If you return to the UK before it expires, no problem.
Why put off renewing it anyway? The new one will be dated from the expiry date of the old one, so you won't lose any time by doing it now. I would suggest getting it done now anyway...why wait? You have plenty of time to get it done and returned before you make your journey.