Sounds like you need a plug and lead change to start with!
If you have cracked leads they sound quite old and are probally braking down inside or the insualtion is giving up and they are shorting against the engine, take off top engine cover [if you have one] to expose the leads and see if they are in the plastic guides or are they touching the head somewhere if so it will only take one and you get miss fire as it has melted the plastic/rubber coating and is now shorting against the head, best way to spot it is take off cover in daylight, then when it is dark pop the hood and fire it up then have a look at the engine in the dark, you should see - nothing, if you see blue flashes, then there is the culprit - simples - as that rodent on the TV says.
mine did this so I took a look at night it was like a neon blue light show!, don't buy to low a qulity lead set though, I did and had to change them again 4 months later, off the top of my head a lead set is around £40 I think and plugs around £12 a set, for the 1.2, not sure for 1.6.
Have you had a battery check done on your battery, you may have a dead cell draining it, if the battery is ok then you have a current drain from some where, if you don't use it much or for very short trips the boot light is a good start, it may be 'stuck' on, after market radios/sound systems are another source of drain as are aftermarket alarms if not fitted correctly.
But for your running problem I would 1st change leads, then plugs, and go from there, notihng more anoying when you feel it is going down hill with problem after problem..
Oh yes I forgot to say, if you are changing them, change one at a time, don't pull em all off they need to be in the right order!