When was the fuel filter last changed ?, have you checked the emissions when cold/hot ?
Although 105ps it may well be they are not the lightest cars around, I'm sure it was for the 1.8 zetec silvertop 116PS/114BHP though.
If the fuel filter hasn't been changed in the last 2 years I would do this first, less than £10 probably as well.
tabetha