Hello, hope you don't mind me jumping in. I had experience of my DS not shifting his body clock WU time with the clock change so I tend to spot the clock change threads.
I do agree with Zoe about moving the first nap back to it's original time, I wouldn't be offering earlier because he's already had a few days to adjust but is not shifting.
What worked best for me was to shift everything *beyond* the original hour that it needed to move. Going up in chunks of 15 - 30 mins every day, not waiting for each shift to show itself in the routine but to just keep going until you are the equivalent of 1.5 or 2hrs changed instead of 1hr (make sense?). Eventually my DS's body clock shifted, we were at 1hr 30 change at that point when he finally woke up later. From there I held for a day or 2 then slowly slowly brought things back that additional half hour, not in a half hour chunk but more like 10 mins each day, checking that WU didn't get early again.
Initially you get the OT but my DS would have lived on the shorter night forever and not moved his WU time so the OT would drag on and on and on. With changing more rapidly and beyond the hour he was kind of forced to shift his WU and the result was less OT in the longer term because it didn't drag on for so long.
One of the best things I read about the clock change (so I always pass it on) was to move all their habitual times not just the sleeps, so every meal, snack, activity, bath time etc as these all help them know where they are up to in the day.
I hope that makes some sense. And good luck.