Would the Creche be willing to work with you if you told them you are working on his sleep? He is 12 months yeh?
I'd recommend firstly waking him every day at 7am. I know this is so hard when you are exhausted but it is necessary initially in order to get better nap structure during the day.
He is napping for a good long stretch during the day but if he is waking at say 1:30 for the day, there is too much of a gap between waking from nap to bedtime which then causes them to become overtired and therefore brings more.
This is the routine I would recommend for him at his age.
7am wake up
7:30 bottle if he is still having one
8am breakfast
9am 30 min cat nap (or anything up to 30 mins)
10am snack
11:45: hot lunch
1pm nap for 2 hrs
3pm snack or bottle if would prefer
5pmDinner
6pm start his bedtime routine, bath, bottle, story and bed
6:30 bedtime
I'd initially say bring bedtime early while you get routine going then push it back to 7pm.
I know these times might not suit with Creche but you can tweak them around.
I'm not sure if exact age, is he 12 months?
Does he eat well (solids) during day? I would offer him his bottle if he doesn't take it within 20 mins of being offered I'd move on, try not get in habit of him snacking on bottle throughout day.