We bought the Argos one (can't afford £450 at JL), it's the pine spindle one and DS loves it, last night it had it's first run as a guest double bed and worked a treat. The mattresses arn't great but I figured that with the money I saved I can buy a decent main mattress when DS needs it (small bodies only need soft mattresses apparently) and the guest one will not get a great deal of use so will make do.
It is always out of stock but you can get them to email as soon as it comes in, which we did, I'm so glad I waited.