fairyJo, thanks for emailing me and keeping me updated. Here's the instructions for a border (this isn't the same as what I did on mine but I needed to make the blanket bigger).
At the end of the last row, when you get to the end, turn the blanket through a quarter turn clockwise. You now have the long side at the top and your hook and wool hanging off the top right-hand corner.
Work around the whole edge of the blanket doing just double crochet stitches. This first row is fiddly because you have to join on to stitches which are going sideways and so on. Just try to keep them evenly spaced, I found that a double into the end of each row plus an extra one in the middle of the trebles worked well. For the short sides just do one double crochet into each stitch. At the corners do two double crochets into the same space.
You should have gone round all four sides of the blanket now - join onto your first double crochet with a slip stitch (just chain but put the hook through your first stitch first). Now double all the way round the blanket again, doing one double stitch into each of the ones in the previous row and two at the corners. When you get back to that starting corner again, slip stitch into your first stitch.
What you have now is a blanket with nice solid edges, helps it to stay square. Now the fun part - a frill! Basically we're going to do a last row of stitches, but make them different heights which gives the blanket its wavy edge. So.
Do three chain stitches (these are pretending to be a treble stitch), then do two trebles into each of the next two stitches (skipping the one the chain is coming from). Now do a double crochet in to the next stitch. Can you see what's happening? Keep doing three treble stitches and then one double one, with each stitch going into the top of the next stitch on the previous row. At the corners, you will probably need to do some extra trebles into the corner space to make the border "turn" properly, see how it works out and don't be afraid to pull it back and try again!
I think you will then be finished ... this set of instructions is a bit tricky - crocheting into the top of stitches is harder than doing it into spaces so don't be surprised if it gets a bit slower going! Good luck and I expect a photo :)