As far as I can see, you are on to a winner here.
In the post you made it clearly states that the guarantee covers "faulty workmanship and faulty materials " as regards the "Base"
It is clear that the "Main Contractor" has used his "Approved Installers" to lay your tiles.
Given you did not appoint the tiler, the "Main Contractor" did that in turn means ALL aspects of this "Slab" must include the tiling and it follows that there is a 10 year Guarantee for the Piles, Slab, Manholes, and Tiling.
If the contractor continues to deny responsibility then get on to Social media and blast them on Face book + Twitter Etc, but warn him of your intentions IF?? he prevaricates.