Use pokerstars man...pokerstars.com
Problem is, I started playing for fun on there...then moved onto money games. I would recommend learning the basics by playing for fun...but dont do it online...The people you play with make stupid calls cause it means nothing to them...so therefore, you dont really learn the actuals of the game. Also, Ive always found when playing for fun...the amount of dodgy river turns and te amount of all ins, makes the game annoying and a put off.
Get some friends together for a friendly game...then put 25 quid online, and see what happens...yeah, you might lose it...but you might not...youll learn a lot quicker when your money is on the line lol