Battery replacement straightforward and no dramas. I had done the pre-reading (i.e. this guide and all the comments) and was ready for the black/gold bit to sproing across the room, which it didn't. Steps very easy as above. I removed the black/gold thing from the phone while I was taking the old battery out so I didn't lose it.

All went back together smoothly - I used a couple of toothpicks to align the black/gold thing + the connector from the battery before screwing them in - the ribbon on the connector was stiff and I was reluctant to be too heavy handed trying to force it in. So gently pushed it into place, screwed back in, back cover on and away we went.

Phone came back to life with 75% battery life and found my network with no dramas. All in all done before the children could come and have a look at what I was doing (10-15 min tops).

Many thanks - now to repair the broken iPad glass.