Very first solo was in a Slingsby Grasshopper with the CCF in 1966. Very short flight, about 100yds.
After that, my first real solo was on a Flying Scholarship at Shoreham in a C150. Arrived on Monday morning for some admin and ground school. Started flying that afternoon. Went solo on the Wednesday early evening after two and a half days and 5hrs 20 mins. Great July in 1971, 35 hours flying in 3 weeks and a PPL at the end. Continuity was the secret to success.
Best ever first solo was in the Hunter F6. Nothing will ever better the fantastic memory of power and freedom.