On the IPhone the alert for a text alert is just a couple of horn toots, or a short bell ring etc....and only lasts a few seconds and half the time I don't hear them.

Is there a way to get a longer tone or perhaps use an MP3 or other tune from your music collection?

I managed to use a song off my phone for a call alert after advice in a previous thread so is it possible with a text alert?

yes you can use custom txt tones.
you can add them the same way you add custom ring tones.

How do you set them please

http://www.macrumors.com/2011/10/13/...ext-tones-too/