Right, after teaching myself how to crochet a Granny square, I am pleased to say I have finished one! It is 8 'layers' (correct term? Not sure) including the centre one.
The videos I viewed online to learn how to do this seemed to make the squares too small and tight, so I adjusted it. The original chain to start off was 6. Each new layer was a chain of 4. Corner chains were 4, and side chains were 2. It has made a much more satisfactory sized piece. I will post a photo on here ASAP! I plan to do another one the same size, but in green and make it into a cushion for my lounge.