I've taken a few photo's and will post them here, along with a little description, in order that you may see what i've done. You are then welcome to copy, or modify, what i've done to achieve something similar for yourself.
Along with a few tools, screws and some really strong grab adhesive, you'll also need some drawer slides and some new, stronger, battens for the bed frame to sit on. I had a mate knock up some 1530mm L x 55mm H x 32mm W timber battens. The slides are 53mm high, hence needing to put higher, 55mm battens in compared to the original 40mm ones.
I bought my drawer slides from Solmer, as they had the best price. I bought some Accuride 5321, 550mm, 150kg rated slides, and I also bought the extra mounting brackets to make attaching the base board and new from trim board a bit easier. You can do it without the brackets and probably get a lower weight rated slide, but i've gone for the belt and braces approach,
http://www.solmer.co.uk/groove-side-mou ... nners.html
http://www.solmer.co.uk/groove-side-mou ... ckets.html
First off, once you've removed the mattresses, you'll be faced with this.

See those little brown caps? They're decorative covers for the screws that attach the front trim board to the bed frame. To remove these, prise off the caps with your finger nail, or a pick. They're held on with a little blob of glue, which is a right bugger to get out of the pozidrive screw heads in order to remove the screws.

Once you have the front board off you'll see this. These are the plywood rails the bed frame is mounted on. They're both too low, at 40mm, and not strong enough to attach the drawer slides, so they need to be removed.

Start unscrewing all the screws you can find that attach the bed frame to the support rails, and also remove the metal heater guard, and you'll end up with two plywood frames.

Remove these frames intact, you'll see why shortly. Once removed you'll end up with this.

Now, using the original frames, measure your new battens and note where the existing screw holes are.
Drill new holes in your new battens, in the same places as the old ones, then add a third hole in the middle of each batten, finishing off each hole with a countersink.
Then, using the original frame as a template, line up and mark where your new battens go.
Attach the outer two battens using six, 6mm x 70mm, torx, countersunk screws. Once these outer battens are in place, your original frame work can be used to help secure the remaining battens.
These four battens will be the bearers for the slides, so will require grab adhesive as well as the three screws, to attach them to your camper and ensure they don't come apart when leverage is applied to the slide-outs.

That's as far as i've got today, more later once the grab adhesive has cured.