I figured out how to sew in the centre panel! Or rather, I looked back at the instructions and had an 'Oh!' moment. In one of the instructions, where it tells you to stitch over the tailors tacks to reinforce the fabric, it shows you a picture of the reinforced dots AND the clipped seams. It doesn't actually tell you to do it so I didn't.
At least I'll know for next time.
Also, I went to a car boot sale this morning and picked up a couple of things. I believe the books were 50p each but the sewing pattern was a real steal at 10p! It's not really my style but it was so cheep I have to at least give it a try.