The Bugatti was a race aircraft and not a combat aircraft. Yes it could go fast but was useless in combat.
The Spitfire started life as a racing plane design in 1931 based on previous successful designs, the actual Spitfire was demonstrated in 1936 and went into production in 1938.
Given that this 100p was still not even flight worthy in 1939 it seems it would have needed five to ten years of development to turn it into a production combat aircraft.
Even the Mustang P51 took four years to go from concept to production and that was a major manufacturer under war conditions with government backing.
It's a fantasy, there's no way an aircraft that was so experimental in 1939 that it couldn't even fly could have been refined, militarized, produced in reasonable numbers and trained for in time for the Battle of Britain.