Hi Kirstym,
My LO is same age and used to Sleep through and now wakes - no idea why - routine is near identical to yours (pre dropping to 3 bottles as haven't got around to that yet). Thinking from the number of posts currently on the NW board of 8 mo's who have started waking I think it's a common problem!
My LO has managed 2 nights of STTN in the last week so hoping the phase is passing!
THanks for the 3 bottle routine - looks great!