2m high wall

I'm building a series of raised planters in 21.5 wide hollow dense block that will be rendered and painted.

In the middle I want to build a 2m high x 1.35 wide wall (3 blocks x 9) using the same blocks with a waterblade feature in the middle.

Searching the net implies that anything over 1m needs professional design. As this won't be weight bearing and only needs to look nice, can anyone foresee a problem if I make sure the foundations are more than adequate?

The problem is if not done properly it could fall on someone. Also if water gets into the structure and freezes that will also weaken the structure.

Whilst I cannot give you any definitive advice (really because I don't want to be liable if anything goes wrong in the future), I will say the following:

In general a 2m high wall should be double skinned as a single skin will not have the required stability, a strip footing of about 500-600mm wide extending past each end of the wall, dug to a suitable depth of around 500mm, with concrete depth of 175mm.

All the above is depending on the ground as local conditions may affect the requirements.

At the very least you will need to set reinforcing bar into the foundation to go through the blocks and then fill the hollow blocks with concrete.