Zen83237 wrote:
I did my drive 10 years ago with a pattern that use standard 200x100
blocks and 100x100 blocks in a different colour.
I didn't realise at the time that the 100x100 blocks where the thicker
blocks. That made it a bit of a pain to lay but it was finished ok.

I now want to dig up the front lawn and lay blocks over that. I don't
want to use the same pattern as before so I want to relay the
existing drive with a new pattern.

I assume that I can lay the new drive higher than the exising drive
then tamp it down to same level. Do I assume that the exising drive
wont tamp down any more so I simpley ralay the blocks on the old sub
base. Then tamp them to settle them in.

I will have to fill in the depression left by the 100x100 blocks
though.

No.
What you'll have to do is remove all the old blocks, and the sand that is
underneath them, and put them all to one side, then buy more hardcore, whack
that down level with the existing hardcore, then re-sand and re-lay all the
blocks (both old and new) on top, getting rid of the thicker blocks first of
course.