Why can't i buy my house?

Hi, about 5 years ago i sold my house, and have been in rented ever since, being on my own i have decided to to buy myself a little flat, have done all the nessessery paperwork, and the date for completion was fixed for Monday next.. now as this house purchase was being a cash buy, i now find that i am not allowed to buy this property unless i can prove where i got my money from,, now the only thing they will exept is proof from the bank of this house transaction some 5 years ago.. i have been to the bank and they tell me it will take up to 2 months to get a statement from so long ago... This sale needs to be completed within the next 3 weeks, otherwise the sale is off.... any suggestions regards this matter would be appreciated,,,, Its a sad world when you can't use your own money as you want... They talk about money laundering, it would appear that he only money laundering is being done by M.Ps in government... Dave