It sounds like you are making great progress
Great nights! and the naps in the cot are so much better too
I think he is just over 10 months now, yes? It is extremely early to be dropping to 1 nap. It's not totally unheard of but very uncommon. Even dropping to 1 nap at 12 months is considered early.
2hrs sleep in the day will be fine. Most LOs would do one short and one long but if he does 2 naps and they are both short AND his mood is okay AND he is sleeping through the night...well...you can't really ask for more I don't think
If he is okay with it then I think you can feel confident that it's okay.
You might put him down for BT a little earlier if he totally refuses an afternoon nap or it is only say 30-40 mins, this will increase the night length (and you will be less likely to need to wake him in the morning) and help to make up for the skipped or short afternoon nap.
One interesting development and we’re not sure if he is just trying it on, he has decided that he wont go to sleep in the afternoon nap
Although it sounds like he is doing well, I would try to avoid totally missing the afternoon nap at this stage. If he won't go to sleep get him up, do another 15-30 min A time and put back down again, even if it means waking him up to preserve BT.
Another thing, capping the morning nap at less than 1hr could help to keep the afternoon nap going. If he is UT for the afternoon he might go down with a shorter morning nap and a little more A time between.
We site on a chair next to the cot and whisper his sleepy words and he eventually goes off.
You are still sitting in the room.
Come on, time to make the next step
...if you want to go slowly that's fine, perhaps it suits you and your DW better.
So move that chair a couple of steps away from the cot. Do just as you are doing but from farther away. If you need to get up to put a hand on or pick up at any point (esp teething, illness etc) that is totally fine, then back to the chair.
After 1-2 days move the chair again.
Depending how big the room is you will be aiming to be out the door in say 1 week.
Chair outside door, you can use verbal reassurance if needed.
I advise you also reduce the verbal reassurance even when the chair is still in the room, so it comes intermittently, increase when needed and decrease when you can. Aiming to be silent as he goes to sleep.
In a week or so you should be able to put him down say your key phrase once, move out of the room, and say nothing else - go get a cup of tea!
Another interesting aspect is that regardless of how much sleep he gets during the day (odd time only 30 mins) he manages to sleep fine at night (touch wood), which i find strange as surely sometimes he is over tired?
I think you are just very lucky that the missed naps don't seem to effect his night sleep. Mine was and still is (at 6yo) very sensitive to loss of sleep. Even 30 mins late to bed causes us night disturbances.
hope this helps