Laying a patio over existing base

[tarairving]

We recently had our old sandstone slabs taken up ready to be replaced with a porcelain patio. We have been told the existing base is solid enough to just tidy it up and relay new slabs over the top. I am not convinced. Images attached. Any advice would be appreciated. Thank you.

 

[MisterBoy]

What makes you think it isn't good enough? Were there problems with the old stones?

 

[tarairving]

Thanks for your reply. This is the old patio. Other than weeds and slightly uneven in some places, it was fine. I am being wary and more want to check that this is something that other people would ordinarily do?