The truth is a candlestick phone is not worth anything like £400 here in the UK. Just the candlestick bit is about £80 untested. £120-£140 if you want it complete with the bell box.
He's still wated his time though if he's trying to sell it for £75. The value is proabbly more like about £15 after conversion. Should be possible to convert it back though, as someone did a while ago, if only I could find that thread.