Constructing Boundary Garden Wall - 30m long 2m high

[confreg]

Hi just looking for some tips please (complete novice): we want to build a wall 2m high and 30m long. Blocks + render would match the house's rendered appearance, and cheaper than bricks.
How wide should the wall be?
Also how deep should the foundations go?
We're in an area of heavy clay soil with a high water table so will also need to put in some kind of damp course....How is this best done?
How frequently should the piers be and what kind of size for them?

Any tips for how on earth to do this on a budget of only £3k?! Yes wooden fencing would be cheaper, but we don't trust the neighbours to not drive into the fences/'accidentally' kick them as they walk past (hence the reason for a 'no messing' wall)....

 

[freddiemercurystwin]

Where are you in the country? As the exposure has an effect on how high a certain thickness of wall should be limited to.

 

[confreg]

We are in Thanet, East Kent, about 3km from the sea; its a very exposed site....It's flat land with no buffers between us and a 'fresh' breeze from the English Channel!