I did 38 metres of retaining at my old place, using reconstituted limestone blocks. Hell of a lot of hard work, with lots of favours called in and lots of favours still owing.
I needed it to look good, so it was pretty much the only option.
I live in an area that is very hilly, close to the beach, so retaining is everywhere.
The thing with retaining is that it needs to stand the test of time. You can retain a fair bit of sand with the old fibro super-six fencing, but it will only last a year or two before leaning or cracking, and then you have made the job twice as hard.
Plenty of people around here try to get creative and try to save bucks on a cheap retaining wall for their holiday home, which is fine if they know what they are doing, but too many end in tears.
I have had a few mates go the way of post and rail concrete, the stuff that is pre-set to size, and you put it up like a fence. This stuff will certainly do the retaining, but in my opinion, looks bloody aweful!
But hey, if its a holiday house or you are planning to put a shed up in front of it, looks don't matter.
My advice to you is to look into the cost of getting the limestone from a supplier, rather than from a shop. Also look into seconds, as you can save a fortune on this. I saved a heap of money by using coffee-rock behind the wall, and tying it in with 10mm s/s bars, shaped into U shapes. I can explain in more detail if you are interested.
My wall was 1300 at it's highest point, and I needed to get Shire approval for this. This was important to me as I wanted to sell the house in a few years time, and not having approval can halt a sale.
Anyway, goodluck and happy seeking, hopefully someone will come along and give you some advice that will be exactly what you are after!
retaining wall alternative 
