I decided to try an alternative method of protecting my pots before they go into the cold greenhouse. After speaking to my friend Peter Fraser, I decided to use a layer of leaves to provide frost protection while the pots are in the coldframe. Before covering the pots with leaves I spread rokolene shade netting on top of the pots, the idea being that I can just lift the netting complete with leaves and not be left with a tidy-up job in the coldframe. I'm guessing this is not a new idea but the thought of filling my coldframe with peat/compost and then emptying it at a later date did not seem such an attractive proposition. I'll know if it works sometime in January 2013. 
If anyone  has used this method I would be interested to hear about your experiences.
Pots spread out in cold frame and watered Rokolene netting placed over the top of the pots
Leaves spread over part of the netting Job done - 3- 4 inches of leaves covering the pots
Frame tops in place. With minus 10C to minus 15C not uncommon I hope this will be adequate protection for the next couple of months.
copyright Paul Barlow 2012