setlocale madness... please help!

I have a debian box, I have just added a bunch of locales using the following command: dpkg-reconfigure locales before I added more locales the only installed locale was 'nl_NL@euro'. my php version is 5.1.2, now for the madness: 1. running the command 'locale -a' returns the following [shortened] list: C de_DE dutch en_GB nl_NL nl_NL@euro nl_NL.iso88591 nl_NL.iso885915@euro nl_NL.utf8 nl_NL.utf8@euro POSIX 2. running the following from the commandline returns "en_GB" (meaning the locale was set correctly) php -r 'var_dump(set_locale(LC_ALL, "en_GB"))'; 3. running the same code via the webbrowser (it is Apache2 and yes I have restarted it!) always returns FALSE (meaning the locale was not set correctly) in fact I can set any installed locale I want on the commandline BUT trying to set any other than the originally installed "nl_NL@euro" in code running via Apache results in FALSE being returned and the locale not being set. has anybody got a clue for me? TIA.