Emma - as you know we have been/are in the exact same position. At the end of July H started refusing naps in bed and it went on all summer. He would sleep in the car even as early as 11am but not in bed. 10 days ago I decided enough was enough, his behaviour was appalling and he was falling apart, we all were. I enforced quiet time in his room from 1-2pm every day. He has a quiet time box with a few little bits that he only has at this time so stickers, paper, a small tractor, a book.
Yes he did not like it and yes he was not quiet to begin but after great advice from Mashi and Shiv and others who had been through it I persevered and he has managed it. He has also slept 4 out of the 9 days he has been up there so far. His behaviour is already better.
He always says he does not want to do it but we just carry on and I put him in his room. On occasion he gets too loud (M is right next door) and if reminders are not working I just tell him I will have to close his door (which he does not want) and he settles back again.
I really had to get to desperation point to do this but I am really glad I did - I hope he keeps it up until he can cope without the nap as clearly he can't right now.
Being on the sofa did not work, he just faffed about, talked to us all, wanted to play etc.