@Allthehotchocolate My Springer is probably a month older than your lab? 6mnths now).
She can cry/growl/bark at bedtime, and after I've made sure she's toileted, I hang around to sometimes give her a cuddle and gentle strokes to settle her, or if she settles and then realised I'm trying to sneak off to bed, I hang around and gently 'shh' to let her know I'm there, and I know when she's ready to sleep as she lets out a deep sigh.
In the morning - or previously during the night - if she's making noises, or barking, I take her out to the garden to wee then bring her back in again with minimal calm interaction, into her crate, and she will settle quite well - even around 6am. A gentle reassuring cuddle or stroke of the neck and chest may be needed. She will then have her breakfast when we're good and ready! Usually about 7:30-8.
So I think make sure they don't need the loo, be calm and quite strict, reassure; no fun, food or fuss until you're ready. Hopefully he will get the idea as you show him the morning routine he needs to adjust to.
I wouldn't leave him to cry though - they are still growing up and I think need reassurance that you're around and will come if needed.
My pup has not taken advantage of this approach!