Yep, 'Bill's Limo' was tough and without the strategy guide, I had to work out that the enemies had to be dispatched in certain order. Still took multiple attempts, and I was on the point of giving up on the game because of it.

You might be able win the 4th mission by just flying straight to the landing airfield before those enemy planes get to the ships.
Anyway, great series. You notice a lot more when someone else is doing the hard work...