Thanks for the advice.
Well after a EW at 4.00am and another at 4.20am, I decided to try limiting the nap even more and put him to bed really early to try and break the EW. Yesterday he only had 20mins sleep after waking at 4.20am (craczy I know) and he was fast asleep at 5pm (unsuprisingly). BUT he slept till 5.30 which is still ealry I know, but he had 12.5 hours which compared to his usual 9 is a big change. I'm going to see how today goes, but I'm hoping that another early night will help to get him back on track. I had tried the big nap but it didn't really work. I generally feel a lot more positive now so thanks for the help.
I do think that he doesn't need much nap time. He went from 2-1 nap at 10 months so has always needed less sleep than recommended, so I think I will keep flexible on this but keep it minimal and see how he copes.
Cheers,
Wendy