Sleep help (please)

Hi, one very tired UK mummy here.

My little one wakes up at 4:30 every single morning, please does anyone have any advice? Its been going on for 4 months now and I am absolutely exhausted, I work full time and so really need my sleep!

I have tried absolutely everything, his room is pitch black, I've tried white noise, night lights, leaving him to cry it out (going in every 10 mins but he never settles even after an hour), moving bed time later, moving it earlier, I just don't know what to do 😭

He is having 1 nap a day about 1 hour long, he does still really need this else he's falling asleep on the floor by 4pm (I tried cutting the nap out).

Hoping someone here has gone through this and can offer some words of advice / support.