From the original post you don't mention that this floor is actually on an decoupling mat! In which case I doubt if Genisis or Dural will be forthcoming with any advice. The injection companies will charge over a £1000 just to look at it and the answer would not be cost effective.
For a similar area with failed decoupling it would be in the region of 9k!
From the view I got through the grout I raked out, I could confidently say that there is no decoupling, and with the state of the tiling I would probably guess that the 'tiler' had never heard of a decoupler anyway. I only need the number of the company/s that Genesis or Dural have used to carry out the resin injection TJ. The 9k is slightly more than I estimate to rip out and replace anyway so possibly not cost effective.
Cheers for that TJ, up bright and early every morning as ever