Edge plinth and insulated basement wall with building blocks, stone, brick or...

[Albireo]

Hello!

I thought it was a simple question!

I am in the process of extending an existing basement under a house.
The Foundation
Planning to fill 0.1m with gravel under the floor insulation and the edge beam.

The Edge Beam
To complete the project, an edge beam needs to be cast. (about 15m)
It will probably be 0.6 - 0.7m wide and about 20 - 25 cm high.
I haven't yet calculated how much reinforcement is needed. - (Anyone know?)
The volume of the edge beam will be 2 - 3m[SUP]3[/SUP]
What is more cost-effective?
Buying a ready-made edge beam, including filling with reinforcement and concrete, or to build a mold and mix the concrete myself? (how much does a mixer hold?)
Does the brand of ready-made edge beam matter?

After the edge beam is complete, a wall will be built. (with openings for doors and possibly some light entry)

Basement Outer Wall
When I came to the material the basement wall should consist of, the questions became more than the answers.

I have called a number of suppliers of various stones, blocks, etc., e.g., Weber, Finja, Jakon, and others, but have not received any answers. Everyone seems to respond with something like: "ask our retailer, We do not answer such questions."

The retailers I've called have, in turn, referred me to a constructor. ("We don't know about this...")

The constructors I've contacted have not had time - e.g., "Check back in 6 weeks."
However, they cost more than I thought. They provide building permits, etc., but the project is so "small" and a building permit has already been issued based on the sketch I have already submitted.
And they only provide their solution with their "blocks". Maybe I need to get drawings and material lists from several constructors to get a good basis for decision?

I just wish to get an answer on:
Why not build the basement wall with, for example, H + H cellular blocks? (what insulation do these provide? - same as Weber Lecablock, Leca isoblock or similar? or why not Finja's Insulated Block Exact?
(In Finja's instructions it says "For masonry of walls below ground or in demanding environments, contact Finja for instructions." but as mentioned they do not answer these questions to private individuals.)
A solution I thought felt good was to cast the wall with thermoblocks and products from Jakon, but encountered considerations that no one wanted to discuss with me.

What's to be built is not very long. But the "last round" will be a challenge; it should end under the house's sill.
For a long time, I thought the thermoblock would be perfect. On the last round, concrete is sprayed in through holes on the side of the blocks until the concrete fills under the sill. But for me, it would mean 3 small loads with the concrete truck since the height of the wall cannot increase too quickly and the volume is limited—if I understood correctly, the transport costs would be very high for me (I am 5-7 miles from the nearest concrete station).

The fundamental question remains:
Which stones/insulation materials would solve my problem and are most cost-effective to use since the wall needs to be insulated?