Thank you so much for this thread; I bookmarked it as I knew I would have to renew my passport in the New year. Collected paper forms this week, took a look and thought too complicated, I'll try online.
Went to Timpsons this morning, photo done in 5 minutes, the man adjusted it to frame, sent it to the passport office online for approval, all ok, printed out photos, gave me a memory stick and also the code to upload it.
Came home, found website, took me 10 minutes to complete, put code in when prompted and the photo appears as if by magic! All done and just got to send old passport back.
Many thanks again!