Is he using them correctly? I.e. leaving them switched on at the wall, making sure the input/charge control is set according to the weather, making sure the output control is set to Min before bedtime and opening it gradually throughout the day so the stored heat lasts?
Cheers for the replies everyone. He's not actually in the flat yet until it's ready, and as I say unfortunately we have no experience of storage heaters.
He'll be at work everyday so only at the flat from the evening onwards - that's why we're trying to find a more economical solution to the heating such as my initial thinking of putting a socket on the Eco 7 ring so that ovenight he could plug in a cheap oil-filled radiator with thermostat and get the cheaper Eco 7 rate plus the flexibility of only a short time to wait until heat is outputted from the rad from switch on as opposed to the storage heater, which I imagine would take a while to output heat from cold?
Also can anyone definitively confirm that regs don't allow sockets, even with individual MCBs, to be directly wired to an Eco 7 consumer unit? Just yesterday a spark didn't say it would be a problem when I was arranging a time for a quote, so am proper confused again, aarrrggh!