Are you serious?
A five digit number becomes complicated and confusing by the addition of one more digit...which is always either a 5 or a 0?!
Do you get confused between flight level 35 and flight level 350 too?
Thread drift,
Lord SM, if you've done some human factors in terms of short term memory you should know that the magic number is 7.
One, two, three, decimal two, seven, five uses it all and doesn't leave space for heading, speed and/or altitude changes to be included.
Also the fact you've done 15 yrs around London doesn't mean everyone has, some of us fly in Europe less than once a month.
The brain also uses chunking in short term memory such as twos (1,2) threes (3,4,5) and fours (5,6,7,8).
132.475, two chunks 3247 one, leaving more short term memory for HDG / SPD & ALT in the same instruction.
Now lets talk about fatigue ...............