Just to pretty much reiterate what other people have said....
you got 3 serious errors, even if 1 of them was a bit iffy, chances of none of the 3 being deserved are pretty slim tbh. You should have been offered a 'debrief' of your test result at the end (with your instructor as well if you wanted) which would have meant you understand where you went wrong. It is worth bearing that in mind if you fail another test at all, as it is def better to know why you failed.
Appropriate speed, means just that, a speed appropriate to the conditions and circumstances. The speed limit is only the max, not what you have to do. You say you drove almost at the exact speed throughout, chances are then that you were doing the speed limit somewhere where you should have slowed down (bad corner, parked cars, a lot of people in a shopping area etc, bad weather - lots of things!). You need to alter your speed to fit the conditions, so time you may be ok doing 40 in a 40 zone, then even an hour later you may not be ok doing 40 as there is now a parked car on a bend there etc.
You need to look at what your other serious errors were for as well, and see what you need to improve on before retaking your test.