The difference between the PPL and the CPL is that the PPL flies for fun/no financial gain. The PPL holder will 'get away' with the occasional airspace breach with a CAA slap on the wrist or an ATC shrug.
The CPL/ATPL pilot is, generally, not so lucky. They fly for financial gain/recompense therefore they are, quite rightly, expected by ATC to be ahead of the game and up to speed in respect to navigation and airspace awareness. That is not to say that the CPL/ATPL holder is immune to cock ups, I know I certainly am not, it's just that there is far more at stake if you do cock up in a major way.
The CAA examiner was quite right to fail your mate on the Nav for that unless your mate positively vocalised his awareness of the close proximity of controlled airspace. You have to remember the examiner can't see inside your head and if you don't tell him what your doing and what your thinking then he can't second guess and will generally draw the worst conclusion. Most guys are there to pass you, but you do need to help them. It's the same in the airline world, there is nothing worse than sitting next to the other pilot when it's their approach thinking 'what the hell is he/she doing now?' Vocalise and share the mental model, that will help you alot.
Finally relax, chill out and enjoy.
W2P
p.s. Rome was lovely
