I needed to post this as nowhere have I read about wind/stomach issues being the cause of frequent waking in older babies. Fortunately I posted in Aibu and Iggly very kindly replied with the suggestion to think whether my ds (13months) was having this problem.
I realised that when he was waking he was sometimes pushing down on his stomach and sometimes having flatulence as well.
I changed his diet to plainer foods, similar to what he ate when first being weaned. No onions, garlic, chilli. No dairy (I still breastfeed). No wheat or eggs or soy. No green leafy veg or beans.
Within a couple of days he was sleeping so much better! Waking once around 3 or 5am for less than an hour. He is also sleeping later for the first time ever! I have been waking before he does, as he now wakes at 7.30-8.30am!
Before this he was waking every hour or 2 during the night and sometimes taking 2 hours to go back to sleep. It might be worth mentioning that he did know how to resettle himself to sleep as he goes to sleep for day naps and bedtime from wide awake with no problem, it was just resettling himself at night that was the problem.
I am feeling so much happier! It has only been a few days but I am so hopeful it will continue!
GP will refer him to dietician so I get some help with reintroducing foods and so we can find out what is causing the stomach problems and so he can be sure to get a balanced diet.