Building a conservatory base is a job that is often undertaken by the enthusiastic DIYer, here is a tutorial to point you in the right direction-
The first step is to Layout footings with string lines and profile boards.
Then Dig the footings to required depth (at least 450mm).
Set pins in sides of the trench to indicate the top level of the concrete when poured.
Pour concrete to required depth (at least 300mm) until it reaches the height of the pins inserted earlier.
Lay the cavity block work.
Internal block work up to underside of block/beam height.
Cover over site with polythene to prevent weed growth.
Then Install block & beam flooring.
Then Grout blocks to lock the floor together.
This is the Base complete awaiting top side.
This is the conservatory being built on the base
This is the almost complete conservatory