Brick or rendered block - Replacement garden wall

[Seasiders]

My garden wall blew over in October 2013, it was 11 metres long and at it's highest it was 2.75 metres. It's on a slope next to a little lane, it starts at 2 metres on both sides and stays at 2 metres on the house side but goes up to 2.75 metres on the road side so is part retaining wall. It was part single skin brick, the highest part, the rest was double skin for half of the height and single skin for the rest. It was apparently rebuilt like this having originally been all single skin with a few single brick piers. The newer double skin wall was perched over the edge of the foundations for the single skin wall.

My structural engineer says that we need new foundations and 300mm width of brick, so 2 bricks laid normally with one sandwiched in the middle on it's side. He did say I could use a Diaphram wall (3 bricks wide hollow but connected through every 5 bricks), but none of the builders I have spoken to have heard of such a wall. The structural engineer is running the calcs to see what width it would need to be in blockwork. The verge between the wall and the road varies from 800mm to 1m so piers projecting out are not an option.

The planning portal says I can replace an existing wall without planning.

How much cheaper would a block wall be than brick (percentage)? Could it be block on the house side and faced with brick on the outside.

If I replace a brick wall with a rendered block wall will I need planning?

I suppose I am hoping that if I build it in brick nobody will notice it's wider than it used to be.

[lutonlagerlout]

are you a southend fan?
if so well done
I have built diaphragm walls but not necessary here
no such thing as a 300mm wall
a brick and a half wall is 335mm but would be expensive
we did one recently similar to yours
215 wide with a 335 pier every 2 metre (inside) and 450 piers at the ends
http://i1110.photobucket.com/albums....6951827
cheers LLL