the story goes sold my rst shell for 1k 6 weeks ago to a guy i know he came round paid £100 deposit said he ould come back with the money pick it up on the monday all good

3 weeks down the line after constant hassle he pays me another 400 and another promise now to today i gave him an ultimatum want rest of money today or i sell it to someone else who is interested im tempted to tell him to fuck off not give his money he has paid back for the time ive had to store the car at mine i feel ive been more than accomidating what would you do ?