In reply to Garston:
Many thanks for suggestions, It is now built and I wimped out of adding the campus board so now have a removeable frame with a finger board on which sits in the space where my loft hatch is so it looks normal when the hatch is in but converts to fun space in about 2 minutes. I should have been a joiner!
I am happy to post a pic if it is of use to someone else who has a houseproud wife and cannot screw boards into walls!
I dont live too far away from Garston, but the name was actually just me picking a name for the internet and I meant to use the ladybird off Ben and Hollys Little Kingdom (I have daughters) but only realised too late its Gaston and I had spelt it wrong! So Garston it is for ever......