As a nanny and night nanny, I would say it could be just his teeth waking him, it can go on for weeks/months! He could be having a growth spurt and waking up hungry.
What is your daily routine?
I would say he needs another short nap about 4pm, just 30-45 minutes. As a PP mentioned, sleep breeds sleep, the more that have, the more they need.
My 8 month old routine is -
7am - wake and a milk feed
8am - breakfast cereal, milk and fruit. 1/2 a slice of toast.
9am - nap 45-60 minutes.
10am - wake, wash and dress.
10:30 - snack (rice cake, fruit, cheese, bread, etc) activity. Class to stimulate, playing/reading at home or in the garden, swimming.
11:45 - lunch (main meal) and pudding (fruit or yoghurt)
12pm - nap for 2 hours.
2pm - milk. Playtime!
4pm - nap 45-60 minutes
5pm - tea, lighter meal, try to avoid protein as this is difficult to digest and may wake him.
6pm - bath with lots of fun play if he's happy to splash about.
6:30 - milk (and a story) with lights low, calm soothing tones!
7pm - into bed awake and leave to self settle.
It does just seem that all you are doing is feeding, changing and getting them to nap but I really do believe routine helps, they learn to expect what is coming and is comforting to them.
I have had 23 charges, all slept through 7-7 (or 7:30-7:30 depending on what routine my employers prefer)
I have been a night nanny to and sleep trained over 50 children with various methods adapted to the parents and they all had 12 hours at night (mostly! Bad dreams, illnesses or wet beds excepted)
I believe it is al down to routine.