I made three major newbie mistakes. I took for granted that my Mist Wallet was the correct version (it wasn't); I didn't test the contract by sending a few ETHs first - I went for the gusto and sent it all; and thirdly I sent the ETC to my Jaxx wallet thinking it would accept ETC - it didn't.  I managed to fix it in the end and I got my ETH and ETC back but it was painful. The guide is perfect - the carbon based life form (me) using it wasn't.