Cockie, re your comment at #24, once the instruction from the across clues has been carried out, and appropriate changes to 1d made, there are not any ambiguities. Before following that instruction there are many ambiguities, of course. I had about 60 empty cells, including an entire entry, though it's possible that some of those 60 could have been filled if I had studied them more closely - it was a bit like solving a sudoku where each cell in a row could be any of five digits.
I was the one who raised the issue of letters in unchecked cells being the same in the initial and final grids. I presumed too much in some cases. I retracted what I said after Keepatit queried me. Sorry if my retraction wasn't clear.