Garden retaining wall for raised beds

[zo]

I am going to have raised beds built all along the boundary of my garden for my disabled mother. The problem is her back garden is against a bridge high above. There is a steep incline with a huge bank of soil bed against it. She would like to level the garden the same height as her current lawn. She is happy to have a high bank against the incline of the bridge. The bank is approx 1 meter high. This would have to have a retaining wall atop which will sit 6 ft feather edge fence panels.

What is the best and the cheapest material to use for this retaining wall, bearing in mind it won't be visible due to the raised flower bed up against it?

How should we build the raised flower bed, which does not cost a fortune but looks good. Sleepers are expensive and I assume they will rot eventually. Bricks or stacked patio stones would look good and can be curved to add interest.

Any advise would be welcome. Thank you.

 

[noseall]

7n dense (solid) concrete blocks - double leaf if necessary.

Shaped or curved walls may have to be done in brick.

 

[r896neo]

dry lock retaining walls are much cheaper than a full masonary wall and will last a lot longer than sleepers but they are not to everyones taste visually.

Tobermore Secura lite is one example but may not be available in your area. it will give you an idea of what they are though and local merchants/suppliers can point you to a similar product