at 4.30am since clock change. It's literally taken us a year to get her to sleep till 5.30 since the last clock change.
This was us! It filled me with dread to go through another 6-12 months of trying to get him to sleep later.
The thing that worked here was to move the routine on more than the hour of the clock change. Basically this
treat it like you were changing time zones about 3 hours, stick rigidly to the new times and wait for her to crash through OT. Not pretty but may help quicker than gradual changes.
Small changes didn't help, we reached the hour later BT and it just meant he lost an hours sleep every night as his body clock continued to wake him at his 'usual' time. What I planned was to shift BT by 2 hrs to achieve the 1 hr clock change, as it turned out I only had to move him 1.5hrs for the crash to come and his body clock re-set. The idea was to shift the times rapidly so he lost less sleep in total as the crash came quicker.
IIWM I'd shift the routine (everything, nap, meals etc) by 30 mins day 1, another 30 mins day 2 and another 30 min day 3 and basically keep going until you get a later WU. When the later WU is achieved the night is prob still short (ie not the 10.5hrs you usually get) so you might then need to move BT a bit earlier again (and naps) to settle back into a routine. I'd be tempted to aim for a later routine anyway, more like nap 3-4 and BT 8 which (based on her night length) would give a possible 6.30am WU, although you lose an hour of Y time in the evening.
You might also think about introducing a gro clock or lights on a timer to help with morning WU although it's not a quick fix and won't solve a 4.30am WU if the routine is off.