I know its frustrating, there isnt a simple solution. If we get a short nap here i cut down the next A time by about 15 mins, if i make it too short then we will just get another 40 min nap.
I think Sarah suggested almost doing set naps so first nap not before 9am for example. It works for some and maybe to get rid of early waking you might need to do the same thing for a week or so.
So say LO wakes at 4.30, but you want to start the day at 5, so you would get LO out of bed at 5 and count your A time from 5.
We have done that when Oz was about 5 month as we were getting EW and nothibg worked to make it better, so if all fails its worth a try.