Is he getting distressed being in there? Or is he more just mucking around and stalling?

If it's the latter, you may find that what worked for us could work for you... We kept the cot in DS's room. I did this initially because I was worried he wouldn't like the bed and we might have to make it a slow transition. But no, he loved the bed. Especially because he could get in and out of it. After a couple of nights we introduced the idea that if he wanted to sleep in the 'big boy' bed then he had to stay in it. If he got out of it three times then he would have to go in the 'baby bed'. We put him in the cot the first night and he hated it. I left him in there for 5 mins or so to prove the point so to speak and then put him back in the big boy bed. Surprise, surprise he stayed in bed and then went straight to sleep. The next night, and most nights after that the threat of having to sleep in the baby bed was enough. For the longest time he would actually say to me 'out of bed, baby bed' when I said goodnight.

HTH