direct to your inboxMoney Saving Expert Martin Lewis says customers who bank with HSBC, First Direct, M&S or John Lewis need to watch out for a specific letter.Speaking on his ITV 'The Martin Lewis Money Show', the finance expert explained how throwing some letters away could be the same as throwing away cash.Martin was sent a message by a man called Andy, who said he had been sent a letter by First Direct with an accompanying cheque for £50.It appears that Andy wasn't the only worried customer