5 YR old waking twice in the night - help!

[PeterParkerSays]

My 5 yr old DS has always been a rubbish sleeper but has been sleeping through more reliably since he started school. However, at Christmas he saw a film that seems to have scared him at night (Monsters inc - he needs wardrobe doors closed "to stop anyone" getting into my room") and his sleep is getting worse and worse. He's also not keen to read stories which have any scary element to them, which never bothered him before, so I'm wondering if this is something to do with his imagination.

I'm torn between "this is utter flannel, he's just saying he's scared / had a bad dream to get in bed with us" vs. "what is he really is scared and we're not taking that seriously". Last night he was up at 12.50, then again at 2.30, when he didn't go back to sleep so I left him to drift off but instead he came into our bed at 2.45, so none of us got any sleep. When he's in bed with us, he seems to need security / comfort - last night I could feel him pushing himself against me so he knew I was there (think "head against mum, check, bum against mum, check, feet against mum, check, now I can go to sleep" as he was doing it in order) and I'll sometimes wake up and find he's climbed in with us and has his legs draped over mine to stop me getting up, or he'll be holding my hand. He's not just after crashing into our bed and then going off to sleep, there is some element of reassurance in there.

I couldn't wake DS this morning, it was like trying to rouse the dead as he was so tired, and DH had to drive 70 miles to work on 5 hours' broken sleep (3 hrs + 2hrs). Generally, I get up with DS on the nights when DH goes to work next day because he has such a long commute and needs his sleep to drive safely. I've even wondered if I should stick DH in DS's bed so he gets a good night's sleep, but I want to sleep with my DH and DS has his own bed and his own room which he has intermittently slept through the night in. There isn't space for the 3 of us in our bed, so I'm trudging around in the day with chronic back ache as I can't move around at night, and grumpy from the broken sleep.

I need some means of getting him to stay asleep, all night, in his own bed, so we can all get a decent night sleep.