Error establishing a database connection

Yep, an oldie but goodie: I have installed WP a few times and not had any probs before, now I’m doing it for a charity, to add a blog to their site but using my own mysql hosting it isn’t working.

username, pw, db name are all 100% correct. Host is streetchildren.jamesspratt.com which I know works as can ping and get to the MySQL admin panel but it doesn’t want to play ball.

Anyone got any tips from the top?

Thanks,

James