recurring issue getting the car to start

[phreaklikeme]

Hi all, first time posting so apologies if this isn't the right part of the forum to ask questions in. 

I have a polo 03 reg, 107k miles, 1.4l petrol, 16V engine.

I've had trouble starting it up a few times recently. I've taken it to garages and they can't isolate the issue. 

I've had the battery and starter motor replaced, the engine oil topped up and I still have trouble. 

The problem is it ticks over when I turn the key, but it doesn't seem to fire up. 

Have any of you had this issue and if so, what was the cause? How did you solve it?