Firstly I'll pay off all my own and my parents debt, their cars and house etc.
Secondly I'll buy myself a decent car and decent house, by this time around 4 - 5 million of the 20 will be spent.
Then I'll put 5 million investment capital in to my company to further expand and grow it.
The last 10 million will be invested long term in unit trusts etc.
Buy a decent car and house
Buy the family a decent car and house
Travel
Invest
Carry on working because I think I would get too bored.
It will be nice to work the usual job stress free knowing you have a crazy amount of money to spend on whatever you want/need