To be honest, while I had a few whitworth wrenches left from my British motorcycle days they are more a convenience than a necessity (except I agree on the seatpost bolt point above); most things can easily be done with adjustable. Modern cone wrenches are also fine and I use them all the time. I would say the one tool that I wish I had was the SA wrench that fits the ball ring on SA hubs - I get by with a punch but the right tool would be great. Everything else though does not need special tools (of course, the cotter press you already have was a wise purchase).