What were you planning to build on top of?
Just an idea: maybe you should consider instead building a row of lecablock around, then fill the gap between with concrete and cast a base over both walls around the whole structure. You could then connect them by strategically drilling and inserting rebar with a chemical anchor in the drilled hole. You can then bend the rebar so they lie in the groove of the lecablock, should hold pretty well.
This might be easier (and possibly cheaper?) than setting rebar, building casting forms, and then casting around the whole thing.
The other work, such as digging out and laying macadam etc., you will have to do regardless.