Seems like everyone is into hint-dropping today instead of actual advice. Maarten's warning is a good one, and refers to http://uk2.php.net/manual/en/function.setlocale.php#25041 where a dutch user had his floating point numbers get mangled going in to mysql because of the differing decimal separator.
Michal: Interesting hint - this is a Zend Framework project so I might follow up on that. Any resources or examples would be helpful, but I will also rummage so many thanks for mentioning this.
Firman: The idea of using an array is excellent advice - quite a few people have recommended that I do this since I wrote this post. Thanks for adding your comment :)