How can I get my 3 year old DS back in his own room?

[Coffeeisyourfriend]

Will try to be brief but not drip feed as its very early and I haven't been to sleep yet (separate issue)
Since the beginning of April my DS has not slept in his own room. The original issue why is not the problem anymore, the problem now is he's just happier being with us. First few weeks I tried everything I could to get him back in his room which mostly ended with him either waking me up 6+ times a night or just coming into our room himself. We gave up trying due to extreme exhaustion and just let him sleep in our room.
In the past 3 weeks, we managed to go from him falling asleep in our bed then moved to his mattress at the foot of our bed where he'd either stay all night or crawl back into our bed to now falling asleep on the mattress but again sometimes crawling back into our bed.
I know he's comfortable on the mattress and is happier now going into his room to get dressed or get toys so I want to try putting the mattress back on his bed and getting his sleeping routine back on track - he's been falling asleep alot later than normal in our room but still having to wake early for nursery so he's a grumpy git most days - but I don't want to ruin what we've just achieved and go back to being woken every hour of the night?
Any advice? Shall I just do it and see what happens or make a fuss (in a good way obviously!) about him moving back into his room and let him help me move the mattress? Should I just keep him with us for a few more weeks or until he's ready to go back himself?

He needs to learn to self settle. When DS2 was having problems he used to fall asleep in our bed to the SleepySounds app, then I'd put him in his own bed.

PerfectlySymmetricalButtocks I think that was one of the apps I tried in the first few weeks, he just kept turning them off and going on you tube so I couldn't leave him alone with the tablet and he wouldn't settle with me there just thought we were having more play time no matter how many times i tucked him in and tried to read him books.
I think he is pretty much self settling now, we all go to bed at the same time now and he gets straight into his bed, we read to him then tell him to close his eyes and go to sleep and he will stay there. Sometimes will sit up and ask for kisses and cuddles from us or to come in our bed but we usually just say to lie down and close his eyes again and for the most part he'll listen unless he's overtired and won't take no for an answer and just gets up anyway.