I didn't change the size of the body of the bag, I just made the strap a bit longer. Actually, a lot longer - so long that you'd have to be fiddling around near your knees to get the bag open :D So I did a cunning thing and looped the strap inside the bag and stitched it. I'm going to get a D ring (is that the right word?) to hook on to the loop, and then give her a little clippy key ring to go with the bag. She can put the clippy key ring on her keys, and then whenever she uses the bag she can just clip the key ring to the D ring, and she won't have to root around at the bottom of her bag for her keys.
The fabric was from Ikea, and I used half a metre, which was the princely sum of 50p in the sale. It was the last piece in the shop, and I'm gutted there wasn't more. I did get some more fabric from the same range but with a different print - much larger and more abstract, but not as good as the poppy seed heads. I just about managed to squeeze the pattern pieces for the outside of the bag on to the fabric I had, so I line it with something else, and I used a linen chambray that you might recognise from Munchkin's Liberty wrap dress.
The project was pretty easy to follow, although I could have done with a few more diagrams and a bit less text, but that's just the way my brain works. I did have to completely reposition the velcro though, even though I followed the instructions on where to place it to a tee.
Only problem now is that I like it so much I don't want to give it away!