Each Level 1 Trade Port provides 2 trade fleets. In addition, your primary port just to the east of London is a Level 2 Trade Port, which provides 3 trade fleets. I can't remember their names, but you basically have...

Level 3 Trade Port (east of London) = 3 fleets
Level 1 Trade Port (Bristol) = 2 fleets
Level 1 Trade Port (Cork?) = 2 fleets
Level 1 Trade Port (Glasgow) = 2 fleets
Total = 9

There's your 9 trade agreements.