After seeing a bunch of gorgeous craft blogs I've decided to attempt making pretty things too. I've glued my craft training wheels on firmly and intend on updating this blog with my creations.
A couple of possibilities. It may be your top thread that is looping, not the bobbin1. that the tensioner of the top thread is not engaging - test this by lowering the presser foot, the tensioning should engage and it should become quite hard to pull the thread through. If the thread still runs freely work the presser foot up and down a bit to free the mechanism2. (and specially if your machine is an elna) the bobbin thread is catching as you begin to stitch. Solution hold both threads back away from the presser foot tightly until the line of sewing is fully established
I would say tension or incorrect threading. Are you SURE you have threaded correctly, including loading the bobbin in the right way round? Do you have the original instructions for your machine, if so dig them out and start from scratch. Also, if your bobbin case has lint in it that can cause it to stick and the bunching begins, so give the bobbin case a clean. Finally check your tension is suitable for the fabric you are working with. HTH.
Just a quick note to thank you both for your help. In the end I got my Mum to show me how to rethread the whole machine again and it worked magic. The joys of being a beginner! Thanks x