My way in was the same as Brendan's. There is only one possible arrangement for two of the 9s, which I solved late on and so was able to fit the answers I had got around them.
I'm always interested in the thematic reason for the jigsaw element in puzzles like this. Obviously it adds an extra level of difficulty, but that alone is discouraged by the editors in the guidance notes. This would still have been a marvellous feat of construction if the clues had been presented normally, but perhaps the positioning of the blank cells and/or the rows to be altered would have been too easy to spot?