Bed guard for use when co-sleeping

[Swaliswan]

I used to accidentally co-sleep with DD when she was tiny so I've decided that this time (DC2 due in 9 weeks) I want to get a bed guard rather than just using pillows/the side of the cot to act as a barrier. Does anyone know which bed guards are good/bad for using with a double bed? I know that they are designed for a single bed so I wondered if anyone had any thoughts on this.

TIA

What about one of those ambi(sp?)nest things that go in the middle instead?

I have a babydan bedguard which fits my king size bed. I got it off ebay. The strap does not stretch all the way to the opposite side but the weight of the mattress and the hooks that go under the mattress keep it perfectly sturdy.
DS is almost 2 and enormous, he can't get the bedguard to move (and he does try very hard!)

Fatcontroller That's really helpful, thanks.

Giantkatestacks I don't want an ambinest for a couple of reasons, I want to breastfeed whilst sleeping and we only have a double bed that just isn't big enough for the nest. I had considered one in the past but I don't want to co-sleep all of the time, just whilst I breastfeed.

i have one, again the strap doesn't quite fit across our double bed so i secure with a bit of string. I left v.early to go to a job yesterday and my fella said when he woke up our 5 month old lo was down the side! (they are meant for use from 18 months) she was fine though and was still chuckling away to herself, he said it was more amusing than anything. It's never happened with me though as i am usually on sleep duties and have always been aware of the possibility and kept her a bit away from the side. On the whole they are great. I have slept better since having one.