Just a point if any of you are considering following my example here are a few tips that might save you a lot of toil & trouble.
When I first made my set up I just found a couple of pallets that fitted inside my coldframe, this was fine to start with! :-\
As many of you will know pallets can be quite heavy and get heavier as they get wetter, plus they swell.
What I found was once they are in the frame you cannot always get a good lift on them because they are at the bottom of the frame, the pallets I used swelled and this made them even more difficult to get out.
So to save me breaking my back every time I did this task I modified the pallets.
All I did was knock the six blocks off leaving what was effectively 'duck boarding' or slatted shelving if you like.
My next move was to make the shelving a little narrower to account for the timber swelling!
I removed the end lath and renailed it without leaving a gap between it and the next lath (beats sawing it down its length).
Now I find I can move them with ease and my back is still intact.
I hope this explanation saves a few bad backs should anyone follow my system.