Can anyone tell me how to do it? Or has anyone a link to a Haynes .pdf?

Its a 52 plate 1.6 Zetec and I've broken it

I broke one on my seat leon and its a right pain in the arse! far better pay someone else to do it imho.
Also you will have to replace the other side too because it will end up pulling one way.

As Gav says, do them in pairs. Also make sure you get a set of springs for a Zetec and not just a Focus as the Zetec has different spring rates compaired to the rest of the Focus range.

Not to bad a job but you will need spring compressors to remove and replace the springs. Iam sure the strut can be removed from the hub so you shouldnt need to disconnect the drive shafts to get the strut off.