Let's not forget that Pam & Winnie did not get lost with directions in Botswana, IIRC, so they are not terrible with directions. Let's also not forget that every single team in the Final 4 has gotten messed up by directions in self driving.
Going back to the stem of the debate, Pam & Winnie would survive the Scotland leg because of catching a better flight than Mona & Beth and Joey Meghan, giving them a 2 hour and 33 minute lead. IIRC, no teams got lost navigating in Scotland (or at least not aired), so I don't believe Pam & Winnie would have blown the lead especially if they don't get U-Turned, thus moving onto the Final 3 as originally presumed.
And FYI, Pam & Winnie only blew a 30 minute lead in New Zealand when they were on the flight by themselves.