that is a mk5 fiesta 99-02. its not a prefacelift mk6, nor could it be a 55 plate. or am i stating the obvious

Definately not a 55 plate! Mk 4 or 5.

That is the MIL (malfunction indicator lamp) and it means there is a fault with the engine that will result in it failing a European emissions test (among other legislative tests). This could be a MAF sensor issue, a problem with the EGR system (if the engine has it), injector problems, a catalyst issue, broken O2 sensor.......

There is usually another light if there is something wrong with the engine that won't affect the emissions (such as a coolant sensor not working, fan broken etc), this is called the PCL (powertrain check lamp). It normally looks like a cog/gearwheel. However in some cars there is not a separate lamp so you get a message somewhere such as EAC Fail. This can be confusing as this is also the primary display for faults with the accelerator pedal (EAC - Electronic Accelerator Control).

Either as everyone has said either take it to a garage asap or try and get a diagnostic code reader on there.