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I agree that the solution is not ideal but he's coming to stay for a week (for the first time, woo hoo) very soon and the bed-stead I bought didn't come with a mattress. The cost of buying a 'proper' mattress at the moment is prohibitive, and I'd rather spend the money on showing him a good time, in any case.
I have inflatable mattresses but have tried to create his own special designated bedroom hence the foam-rubber option.
It's a short-term solution but as so often in my life short-cuts turn out to be not so short, after all............:o)