I can sympahise with as my son (now nearly 5) was the same at the beginning of the year. I tried all sorts of bed layouts - from camps on the floor, makeshift tents over his bed. We knew he was keen for a bunk bed but didn't want to pay an excessive amount and it not to work, but picked one up 2nd hand for £25. It seems to have done the trick although occasionly he will still wonder in but it's not such an issue settling him again. Also, he always takes his lantern/torch to bed with him. I did at one stage wonder if it was connected with him weeing in the night and waking up (as he is still in night-time pants), but the change in bedroom layout has worked for us. Good luck Debbie
