I know it is going to take time, but I would really go and measure the site.
With that many car parking bays, there is going to be oil stains, so how many and how bad are they etc?. Check where the water/stand pipe positions are, then work out hose lengths etc, do you need more hose? Where is the waste water going to go? What is the surface, block or just concrete? On a job this size people will be watching etc, so cover yourself on this issue. Get on to your local water company, check price and whats what for stand-pipe licence. Now can you do this job on your own, or will you have to sub some out? If you sub-out what price do the subbies want per day, and how many metres a day can they clean. also will one stand pipe feed say 2-3 machines? A job this size needs some home work and thought.
Good Luck.