Thanks Claire Honey, unfortunately BT any earier than 12 hours will most likely result in an earlier WU atm, so that would mean his day is longer the next day, unavoidably, so as much as I would like to take it easier on him (you know me

) I don't think it's going to be possible to shift things slowly any more
Most of the time his mood is okay, but on a nap day we get 10 hours, so less than 11 in total, and I know for sure that's not enough, even though his mood isn't bad (he' a very cheers and funny little chap even at 6 am

) he has shadows under his eyes and he can't pass a surface in the house without putting his head down on it. It's also extremely hard to get him to put his dummy away, as when he is tired he wants it constantly for comfort.
Thank you Barbara, that makes total sense to me, and it's helpful to know what F does as they're so similar in age.
Have you tried to offer a nap the day after he had a 12-13 h day without the nap?
Honestly I haven't tried anything purposefully for a while, because he is refusing naps in the house, and car naps depend on our day and the weather, as he won't nap in the car if the sun is out. But there is a chance that if I keep his days at 12 hours (if possible) that he will start to self regulate with naps here and there. However I think I will keep them short if possible, because otherwise his night will be super short and although his sleep will be spread, it could end up being counter-productive, does that make sense

Hugs vicki I wish I had advice hope my hugs are helpful
Yesterday we had a no nap day (planned) Z was fine till ~4/4.30 then a bit cr@p. did BT of 5.45 and he slept till 7.30am! Phew...at least I know the odd day he is ok. I'm thinking maybe 1 a week we do this (weekend) as there are lots of things on weekends during nap time ATM I know he will love YK?
Thanks Sara, (Hugs) to you too. Sam has an afternoon cut off time when his mood goes down hill too, so I make sure we are in the house then, so he can do something low key when he is at his most tired. He seems to pick up later funnily enough, he moves through it.
Today he was up at 6.30 and asleep bang on 6.30. He has been really happy, and in the car twice without napping. He actually fell asleep while I sang to him tonight, bless him. At least BT's are sorted, and the circus act is over for now LOL
If he wakes at 5.30 I have a plan. First I will cry

then I will take him downstairs and put Peppa on while I seep on the sofa LOL

Thanks again everyone

x.