Thanks ladies!
It must have worked because he STTN again and they woke at 7am which is great.
I'm not so sure about tonight as he was super grumpy at bedtime - at only 7pm! Luckily I was able to get them both down early as DH was staying late at work.
I thought he had a decent nap today and wasn't grumpy when he woke, and we had an afternoon at home, but he barely lasted 4hrs between nap WU and BT.
Fingers crossed for tonight and hoping DS1 doesn't wake everyone up early because I put him to bed to deal with grumpy DS2.
He seems only too happy to be left alone in his bed now. He didn't want me to rub his back or anything, just wanted me out of the room and the light off. Can see he's happily waving his muslin around now. Lol. Expect sleep any minute.