Go to B&Q mate I painted my old garage floor which was a large single garage.
One coat applied with a roller and i still had 1/4 tin left. Very gloopy stuff sod doing loads of coats!!!!

They sell blue, light grey or red paint it was around £40-50 quid also.

Stayed stuck too and very hard wearing.

BUT if you have any oil patchs make sure you degrease it well or paint will lift.