The difference between the A1a and A10 types is as NicholasC says, there are letters in the upper corners of the A10 and the plate number is incorporated into the design.
For the A2 and A8 there is no difference in the design. The latter is perforated, the former is not.
There is a 2d blue in the A1 design. The difference is that in the A2 and A8 there is a white line above the words TWO PENCE.
