I, also find myself with the same difficulties.
I too was far too lazy in my last year at School (5th year)
I have 8 standard grades, 6 of which are credit level (2 1's + 4 2's). Of which were:
Geography 1
Accounting + Finance 1
English 2
Physics 2
Home Eco 2
Administration 2
French 3
Maths 3
And are now currently doing 4 highers - realistically passing 3 of them - say 1 B and 2 C's. Will also be doing an AAT qualifacation (which qualifies as an Advanced GNVQ) before applying to NATS.
What would be my chances !?!