If you were in the U.S., I'd say accept the money and donate it all to a charity, thereby gaining the tax deduction and still not "accepting" the inheritance... Probably not valid for U.K. purposes...
By "left" do you mean money which the person is due to receive as a bequest under someone's Will? If so (assuming you are in the UK) the position is that a Deed of Variation can be completed within two years of the death under which a beneficiary foregoes the bequest in favour of a named alternative person or organisation (such as a charity). There is no tax liability (actual or potential) on the beneficiary who gives up the bequest in this way.
What is the position if the benficiary wishes to forego the bequest after a period of greater than 2 years after the death. Could it still be given or transferred to an alternative person. If so is there a liability on the receiving party.