Hi I have a 2002 fiesta. Last of the bubble shape. The other night after driving it as normal when I turned the key it makes a loud clicking noise. A guy who helped me bump it said it was the starter motor jammed. Anyway a few more days have passed and it's been fine. No issues starting, no dimming of lights etc which would indicate a battery issue. This morning my girlfriend has gone to start the car and the same issue. The clicking noise. The lights on the dashboard seem to dim on and off in time with the clicking. Does this sound like a battery issue or from what I've read online a solenoid issue? Which is inside the starter motor? Any help would be appreciated. Complete novice with mechanics. Thanks 

Sounds more like a battery issue, what you describe is pretty common when the battery does not have enough oomph to turn the starter. 

I thought as much but then the car has been starting without an issue early morning after standing all night. And only on these 2 occasions has this problem occurred. All in between it has been fine starting. This is why I thought it may be something else. Thankyou for your help. 

Get the battery load tested and see what it says. Many places who sell batteries will do this for free in hope of a sale. 

not all that likely -but -it could be dirty corroded battery terminals not allowing enough current for the starter motor to turn.

solenoid is fixed to the starter motor, a separate lump bolted on the side of it. the solenoid could be changed without replacing whole starter motor but you would need to get starter motor out of car to do it. I am not sure how easy it is to get a solenoid as generally people just change the whole starter motor including the solenoid. And it is rare for the solenoid to fail , although on my sisters 1990(ish) fiesta the thick cable that links the solenoid to the motor itself (about 3 inches long) corroded through